Obama: Terror threat against US has entered 'new phase'

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WASHINGTON (AP) -- In a rare Oval Office address, President Barack Obama vowed Sunday night the United States would overcome a new phase of the terror threat that seeks to "poison the minds" of people here and around the world, as he sought to reassure Americans shaken by recent attacks in Paris and California.

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"I know that after so much war, many Americans are asking whether we are confronted by a cancer that has no immediate cure," he said, speaking from a lectern in his West Wing office.

The president's speech followed Wednesday's shooting in San Bernardino, California, that killed 14 people and wounded 21. Authorities say a couple carried out the attack and the wife pledged allegiance to the Islamic State and its leader in a Facebook post.

Watch more coverage:

What Does San Bernardino Attack Mean for Terror Fight in U.S.?

Obama said that while there was no evidence the shooters were directed by a terror network overseas or part of a broader plot, "the two of them had gone down the dark path of radicalization."

"This was an act of terrorism designed to kill innocent people," he said in the 13-minute address.

See Obama addressing the nation on Sunday:

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Barack Obama primetime address on terrorism 12/6
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Obama: Terror threat against US has entered 'new phase'
WASHINGTON, DC - DECEMBER 6: U.S. President Barack Obama addresses the country from the Oval Office on December 6, 2015 in Washington, DC. President Obama is addressing the terrorism threat to the United States and the recent attack in San Bernardino, California. (Photo by Saul Loeb-Pool/Getty Images)
WASHINGTON, DC - DECEMBER 6: U.S. President Barack Obama addresses the country from the Oval Office on December 6, 2015 in Washington, DC. President Obama is addressing the terrorism threat to the United States and the recent attack in San Bernardino, California. (Photo by Saul Loeb-Pool/Getty Images)
US President Barack Obama addresses the nation from the Oval Office at the White House in Washington, DC, on December 6, 2015. AFP PHOTO/NICHOLAS KAMM / AFP / NICHOLAS KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)
WASHINGTON, DC - DECEMBER 6: U.S. President Barack Obama addresses the country from the Oval Office on December 6, 2015 in Washington, DC. President Obama is addressing the terrorism threat to the United States and the recent attack in San Bernardino, California. (Photo by Saul Loeb-Pool/Getty Images)
IRVING, TEXAS - DECEMBER 06: Bar patrons watch as President Barack Obama addresses the nation from the Oval Office on December 6, 2015 at the DFW Airport in Irving, Texas. President Obama spoke about the government's campaign against the terrorist threat, following last week's attack in California. (Photo by John Moore/Getty Images)
SAN BERNARDINO, CA - DECEMBER 06: Jonathan Tovar sits with his grandmother Helen Medina in her house, which was hit by bullets as police engaged in a gun battle with terror suspects on the street in front, as they watch President Barack Obama give a nationally-televised address from the White House about terrorism following the attack on the Inland Regional Center on December 6, 2015 in San Bernardino, California. Medina hid in her home as the police killed the terror suspects that attacked the Inland Regional Center in San Bernardino that left 14 people dead and another 21 injured on December 2. (Photo by Joe Raedle/Getty Images)
WASHINGTON, DC - DECEMBER 6: U.S. President Barack Obama addresses the country from the Oval Office on December 6, 2015 in Washington, DC. President Obama is addressing the terrorism threat to the United States and the recent attack in San Bernardino, California. (Photo by Saul Loeb-Pool/Getty Images)
WASHINGTON, DC - DECEMBER 6: U.S. President Barack Obama addresses the country from the Oval Office on December 6, 2015 in Washington, DC. President Obama is addressing the terrorism threat to the United States and the recent attack in San Bernardino, California. (Photo by Saul Loeb-Pool/Getty Images)
US President Barack Obama addresses the nation from the Oval Office at the White House in Washington, DC, on December 6, 2015. AFP PHOTO/NICHOLAS KAMM / AFP / NICHOLAS KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)
WASHINGTON, DC - DECEMBER 06: U.S. President Barack Obama delivers a national address from the Oval Office of the White House December 6, 2015 in Washington, DC Obama was expected to speak on his plans to battle the threat of terror attacks and defeating ISIL in the wake of last week's attack in San Bernardino, California. (Photo by Win McNamee/Getty Images)
A bartender at a hotel near the Inland Regional Center watches President Obama speak on TV during the aftermath of a mass shooting that killed 14 people on Sunday, December 6, 2015 in San Bernardino, California, USA. AFP PHOTO/PATRICK T. FALLON / AFP / Patrick T. Fallon (Photo credit should read PATRICK T. FALLON/AFP/Getty Images)
U.S. President Barack Obama delivers an address to the nation in the Oval Office of the White House in Washington, D.C., U.S., on Sunday, Dec. 6, 2015. Obama sought to soothe a nation shaken by the terrorist attack in a California town with assurances that the U.S. is hardening its defenses that were tempered by an acknowledgment that the threat to the country is ever-evolving. Photographer: Saul Loeb/Pool via Bloomberg
President Barack Obama addresses the nation from the Oval Office at the White House in Washington, Sunday night, Dec. 6, 2016. The president announced no significant shift in U.S. strategy and offered no new policy prescriptions for defeating the Islamic State, underscoring both his confidence in his current approach and the lack of easy options for countering the extremist group. (Saul Loeb/Pool Photo via AP)
President Barack Obama addresses the nation from the Oval Office at the White House in Washington, Sunday night, Dec. 6, 2016. The president's speech followed Wednesday's shooting in San Bernardino, California, that killed 14 people and wounded 21. (AP Photo/Jacquelyn Martin)
WASHINGTON, DC - DECEMBER 06: U.S. President Barack Obama delivers a national address from the Oval Office of the White House December 6, 2015 in Washington, DC Obama was expected to speak on his plans to battle the threat of terror attacks and defeating ISIL in the wake of last week's attack in San Bernardino, California. (Photo by Win McNamee/Getty Images)
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In speaking from the Oval Office, Obama turned to a tool of the presidency that he has used infrequently. His decision to speak in prime time reflected the White House's concern that the his message on the recent attacks hasn't broken through, particularly in the midst of a heated presidential campaign.

Yet Obama's speech was likely to leave his critics unsatisfied. He announced no significant shift in U.S. strategy and offered no new policy prescriptions for defeating IS, underscoring both his confidence in his current approach and the lack of easy options for countering the extremist group.

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Obama did call for cooperation between private companies and law enforcement to ensure potential attackers can't use technology to evade detection. He also urged Congress to pass new force authorization for military actions underway against IS in Iraq and Syria, and also to approve legislation to bar guns from being sold to people prohibited from flying on planes in the U.S. for terrorist concerns.

Still, he called on Muslims in the U.S. and around the world to take up the cause of fighting extremism.

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The spread of radical Islam into American communities, he said, is "a real problem that Muslims must confront without excuse."

The president's most specific policy announcement was to order the departments of State and Homeland Security to review the fiance visa program that the female shooter in California used to enter the U.S. In his remarks, Obama referred to a visa waiver program that Congress is also reviewing, but the White House later clarified he meant the fiance program.

RELATED: See inside the San Bernardino shooting suspects' home

32 PHOTOS
Inside San Bernardino shooting suspects home
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Obama: Terror threat against US has entered 'new phase'
REDLANDS, CA - DECEMBER 4: Inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly the recent mass shootings, lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)
REDLANDS, CA - DECEMBER 4: A Quran sits in the living room inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)
REDLANDS, CA - DECEMBER 4: An identification card for Syed Farook inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)
REDLANDS, CA - DECEMBER 4: A hole in the ceiling could be seen inside the closet area of the rear bedroom inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)
REDLANDS, CA - DECEMBER 4: A baby crib is seen inside the baby room of the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings, lived, on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)
REDLANDS, CA - DECEMBER 4: A firearm lubricant could be seen in the closet of the front bedroom inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)
REDLANDS, CA - DECEMBER 4: Media reporters go in and out of the townhouse where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)
REDLANDS, CA - DECEMBER 4: A praying mat and a cleared out closet in the baby room in the front of the apartment. A rare first glimpse inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly the recent mass shootings, lived, on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)
REDLANDS, CA - DECEMBER 4: Prayer beads are seen laying on the bed alongside personal documents in the rear bedroom inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)
REDLANDS, CA - DECEMBER 4: A closet inside the baby room. A rare first glimpse inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings, lived, on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)
REDLANDS, CA - DECEMBER 4: A rare first glimpse inside the house where Syed Rizwan Farook and Tafsheen Malik, suspects of the deadly recent mass shootings, lived on December 4, 2015 in Redlands, California. (Photo by Marcus Yam/Los Angeles Times via Getty Images)
A book sits on a table inside the home of San Bernardino mass murder suspect Syed Farook, December 4, 2015 in Redlands, California. The community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. AFP PHOTO / ROBYN BECK / AFP / ROBYN BECK (Photo credit should read ROBYN BECK/AFP/Getty Images)
Journalists squeeze into a child's bedroom in the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. AFP PHOTO / ROBYN BECK / AFP / ROBYN BECK (Photo credit should read ROBYN BECK/AFP/Getty Images)
A view of the kitchen inside the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. AFP PHOTO / ROBYN BECK / AFP / ROBYN BECK (Photo credit should read ROBYN BECK/AFP/Getty Images)
A television crew prepares to do a live report inside a child's bedroom in the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. AFP PHOTO / ROBYN BECK / AFP / ROBYN BECK (Photo credit should read ROBYN BECK/AFP/Getty Images)
SAN BERNARDINO, CA - DECEMBER 04: Reporters take pictures of photographs found inside the home of shooting suspect Syed Farook on December 4, 2015 in San Bernardino, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)
REDLANDS, CA - DECEMBER 04: Baby food sits on a kitchen counter inside the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)
REDLANDS, CA - DECEMBER 04: A hatchet sits in a kitchen drawer inside the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)
REDLANDS, CA - DECEMBER 04: Reporters inspect the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)
REDLANDS, CA - DECEMBER 04: Arabic books sit in a closet inside the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)
REDLANDS, CA - DECEMBER 04: An Islamic Manners book sits in a bedroom inside the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)
REDLANDS, CA - DECEMBER 04: A book about prayer sits on a bedside table inside the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)
SAN BERNARDINO, CA - DECEMBER 04: Reporters inspect the home of shooting suspect Syed Farook on December 4, 2015 in San Bernardino, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)
REDLANDS, CA - DECEMBER 04: Reporters inspect the home of shooting suspect Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)
REDLANDS, CA - DECEMBER 04: Reporters inspect the home of Syed Farook on December 4, 2015 in Redlands, California. The San Bernardino community is mourning as police continue to investigate a mass shooting at the Inland Regional Center in San Bernardino that left at least 14 people dead and another 21 injured. (Photo by Justin Sullivan/Getty Images)
Members of the media crowd into the apartment bedroom of San Bernardino shooting suspects Syed Farook and his wife, Tashfeen Malik, in Redlands, Calif., Friday, Dec. 4, 2015, after the building landlord invited journalists into the townhouse. A book containing passages from the Quran is seen at right. (AP Photo/Chris Carlson)
Members of the media crowd into a child's room in an apartment in Redlands, Calif., shared by San Bernardino shooting rampage suspects Syed Farook and his wife, Tashfeen Malik, Friday, Dec. 4, 2015, after the building landlord invited media into the townhouse rented by the California attackers. (AP Photo/Chris Carlson)
Members of the media crowd into the living room of an apartment in Redlands, Calif., shared by San Bernardino shooting rampage suspects Syed Farook and his wife, Tashfeen Malik, Friday, Dec. 4, 2015, after the building landlord invited media into the townhouse rented by the California attackers. (AP Photo/Chris Carlson)
Members of the media crowd into the living room of an apartment in Redlands, Calif., shared by San Bernardino shooting rampage suspects Syed Farook and his wife, Tashfeen Malik, Friday, Dec. 4, 2015, after the building landlord invited media into the townhouse rented by the California attackers. (AP Photo/Chris Carlson)
Members of the media crowd into a child's room in an apartment in Redlands, Calif., shared by San Bernardino shooting rampage suspects Syed Farook and his wife, Tashfeen Malik, Friday, Dec. 4, 2015, after the building landlord invited media into the townhouse rented by the California attackers. (AP Photo/Chris Carlson)
A member of the media films a wall tapestry displaying religous writing in the living room of an apartment in Redlands, Calif., shared by San Bernardino shooting rampage suspects Syed Farook and his wife, Tashfeen Malik, Friday, Dec. 4, 2015, after the building landlord invited media into the townhouse rented by the California attackers. (AP Photo/Chris Carlson)
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He also reiterated his call for broader gun control legislation, saying no matter how effective law enforcement and intelligence agencies are, they can't identify every would-be shooter. He called it a matter of national security to prevent potential killers from getting guns.

"What we can do, and must do, is make it harder for them to kill," he said.

Watch more coverage:

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Obama stands little chance of getting the Republican-led Congress to agree to any gun control measures. On Thursday, the Senate rejected legislation barring people suspected by the government of being terrorists from purchasing firearms. Gun rights advocates say such a ban would violate the rights of people who haven't been convicted of crimes.

Congress also has been unable to coalesce behind any plan to authorize more force against IS, and the administration's proposal has languished since February.

Obama repeated his long-standing opposition to an American-led ground war in the Middle East and made no mention of the more aggressive action others have suggested, including a enforcing a no-fly zone and safe corridors in Syria.

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After the speech, the president appeared as previously scheduled at the Kennedy Center Honors tribute in Washington.

The president's critics -- and increasingly, some members of his own party -- have questioned his strategy. Hours before he spoke, Hillary Clinton -- his former secretary of state and the front-runner for the Democratic presidential nomination -- said the U.S. is "not winning" the fight against IS.

Obama has insisted that the Islamic State is contained in Iraq and Syria. However, the group has set its sights elsewhere in the world, launching attacks in Lebanon and Turkey and downing a Russia airliner over Egypt.

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The Nov. 13 attacks in Paris marked the group's most aggressive actions in Europe, a coordinated effort that left 130 people dead and wounded hundreds more.

Last week, the terror threat drew even closer for Americans when a couple -- a 29-year-old woman originally from Pakistan and her 28-year-old American-born husband -- launched an attack on a holiday luncheon in San Bernardino.

See photos from the scene of the San Bernardino shooting:

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San Bernardino active shooter, scene and police operations
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Obama: Terror threat against US has entered 'new phase'
This July 27, 2014 photo provided by U.S. Customs and Border Protection shows Tashfeen Malik, left, and Syed Farook, as they passed through O'Hare International Airport in Chicago. The husband and wife died on Dec. 2, 2015, in a gun battle with authorities several hours after their assault on a gathering of Farook's colleagues in San Bernardino, Calif. (U.S. Customs and Border Protection via AP)
This undated combination of photos provided by the FBI, left, and the California Department of Motor Vehicles shows Tashfeen Malik, left, and Syed Farook. The husband and wife died in a fierce gunbattle with authorities several hours after their commando-style assault on a gathering of Farook's colleagues from San Bernardino, Calif., County's health department Wednesday, Dec. 2, 2015. (FBI, left, and California Department of Motor Vehicles via AP)
An investigator looks at a Black SUV that was involved in a police shootout with suspects, Thursday, Dec. 3, 2015, in San Bernardino, Calif. A heavily armed man and woman opened fire Wednesday on a holiday banquet, killing multiple people and seriously wounding others in a precision assault, authorities said. Hours later, they died in a shootout with police. (AP Photo/Jae C. Hong)
FBI agents search outside a home in connection to the shootings in San Bernardino, Thursday, Dec. 3, 2015, in Redlands, Calif.. A heavily armed man and woman opened fire Wednesday on a holiday banquet, killing multiple people and seriously wounding others in a precision assault, authorities said. Hours later, they died in a shootout with police. (AP Photo/Ringo H.W. Chiu)
Investigators search for bullet casings at the scene where Wednesday's police shootout with suspects took place, Thursday, Dec. 3, 2015, in San Bernardino, Calif. A heavily armed man and woman dressed for battle opened fire on a holiday banquet for his co-workers Wednesday, killing multiple people and seriously wounding others in a precision assault, authorities said. Hours later, they died in a shootout with police.(AP Photo/Jae C. Hong)
Investigators gather around a Black SUV that was involved in Wednesday's police shootout with suspects, Thursday, Dec. 3, 2015, in San Bernardino, Calif. A heavily armed man and woman dressed for battle opened fire on a holiday banquet for his co-workers Wednesday, killing multiple people and seriously wounding others in a precision assault, authorities said. Hours later, they died in a shootout with police. (AP Photo/Jae C. Hong)
REDLANDS, CA - DECEMBER 2: A SWAT team member stands watch with a rifle pointed at a home being investigated by police is shown after a mass shooting at the Inland Regional Center in San Bernardino December 2, 2105 in Redlands, California. Multiple fatalities and injuries were reported in the shooting (Photo by Marcus Yam/Los Angeles Times via Getty Images)
Law enforcement officers investigate a suspicious bag, later found not to be a threat, on Victoria Avenue after a mass shooting at the Inland Regional Center on Wednesday, December 2, 2015 in San Bernardino, California. At least 14 people were killed in a gun attack on a holiday party, triggering a massive manhunt that ended when police shot dead two heavily armed suspects -- a man and a woman -- on a quiet residential street. AFP PHOTO / PATRICK T. FALLON / AFP / Patrick T. Fallon (Photo credit should read PATRICK T. FALLON/AFP/Getty Images)
SAN BERNARDINO, USA - DECEMBER 02: Yellow stripe is seen as the US Security Forces secure the area following a shooting that killed multiple people at a social services center for the disabled in San Bernardino, California of United States on December 02, 2015. Two suspects in a deadly mass shooting that killed 14 victims at a social services facility in California were killed after a confrontation with police, authorities said Wednesday. The initial shooting occurred earlier Wednesday when at least one shooter opened fire in San Bernardino at the Inland Regional Center, which provides services to persons with developmental disabilities and their families. At least 17 others were injured. (Photo by Mintaha Neslihan Eroglu/Anadolu Agency/Getty Images)
SAN BERNARDINO, CA - DECEMBER 2: A police officer officer guards a police line as officers prepare to raid the home of one or more suspects of a mass shooting at the Inland Regional Center by multiple gunmen on December 2, 2015 near San Bernardino, California. Police continue to investigate the shooting that left at least 14 people dead and another 17 injured. (Photo by David McNew/Getty Images)
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Authorities surround the scene following a shootout Wednesday, Dec. 2, 2015, in San Bernardino, Calif. Multiple attackers opened fire on a banquet at a social services center for the disabled in San Bernardino on Wednesday, killing multiple people and sending police on a manhunt for suspects. (AP Photo/Jae C. Hong)
Authorities guard the perimeter near the location of an officer-involved shooting Wednesday, Dec. 2, 2015, in San Bernardino, Calif., following a shooting that killed multiple people at a social services center for the disabled. (AP Photo/Damian Dovarganes)
SAN BERNARDINO, CA - DECEMBER 2: Police place a marker along E. San Bernardino Ave. where a shootout occurred December 2, 2015 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for suspects still at large. (Photo by Rick Loomis/Los Angeles Times via Getty Images)
Armed police personnel walk along closed off streets in the San Bernardino neighborhood near the intersection of Richardson and Gould where a house was searched on December 2, 2015. A man and a woman suspected of carrying out a deadly shooting at a center for the disabled in California were killed in a shootout with police, while a third person was detained, police said. AFP PHOTO / FREDERIC J. BROWN / AFP / FREDERIC J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)
SAN BERNARDINO, CA - DECEMBER 2: A police helicopter circles as officers search for a possible suspect following a shootout with suspects of a mass shooting at the Inland Regional Center by multiple gunmen on December 2, 2015 in San Bernardino, California. Police continue to investigate the shooting that left at least 14 people dead and another 17 injured. (Photo by David McNew/Getty Images)
Law enforcement officers search for the suspects of a mass shooting December 2, 2015 in San Bernardino, California. A man and a woman suspected of carrying out a deadly shooting at a center for the disabled were killed in a shootout with police, while a third person was detained, police said. AFP PHOTO / PATRICK T. FALLON / AFP / Patrick T. Fallon (Photo credit should read PATRICK T. FALLON/AFP/Getty Images)
A police officer deploys tape to an area near where authorities stopped a vehicle in San Bernardino, Calif., Wednesday, Dec. 2, 2015. Multiple attackers opened fire on a banquet at a social services center for the disabled in San Bernardino on Wednesday, killing multiple people and sending police on a manhunt for suspects. (AP Photo/Damian Dovarganes)
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Law enforcement officers search for the suspects of a mass shooting December 2, 2015 in San Bernardino, California. A man and a woman suspected of carrying out a deadly shooting at a center for the disabled were killed in a shootout with police, while a third person was detained, police said. AFP PHOTO / PATRICK T. FALLON / AFP / Patrick T. Fallon (Photo credit should read PATRICK T. FALLON/AFP/Getty Images)
SAN BERNARDINO, CA - DECEMBER 2: A SWAT unit mobilizes near Richardson Street after a mass shooting at the Inland Regional Center on December 2, 2105 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for up to three suspects who are still at-large. (Photo by Marcus Yam/Los Angeles Times via Getty Images)
SAN BERNARDINO, CA - DECEMBER 2: Law enforcement officers search for a possible suspect following a shootout with suspects of a mass shooting at the Inland Regional Center by multiple gunmen on December 2, 2015 in San Bernardino, California. Numerous deaths and injuries have been reported. (Photo by David McNew/Getty Images)
Law enforcement officers search for the suspects of a mass shooting December 2, 2015 in San Bernardino, California. A man and a woman suspected of carrying out a deadly shooting at a center for the disabled were killed in a shootout with police, while a third person was detained, police said. AFP PHOTO / PATRICK T. FALLON / AFP / Patrick T. Fallon (Photo credit should read PATRICK T. FALLON/AFP/Getty Images)
In this image taken from video, armored vehicles surround an SUV following a shootout in San Bernardino, Calif., Wednesday, Dec. 2, 2015. The scene followed a military-style attack that killed multiple people and wounded others at a California center that serves people with developmental disabilities, authorities said. (KTTV via AP)
SAN BERNARDINA, CA - DECEMBER 2: A search team goes door-to-door looking for the third suspect in a residential neighborhood after a mass shooting at the Inland Regional Center on December 2, 2105 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for up to three suspects who are still at-large. (Photo by Marcus Yam/Los Angeles Times via Getty Images)
SAN BERNARDINO, CA - DECEMBER 02: A California Highway Patrol officer stands with his weapon as authorities pursued the suspects in a shooting that occurred at the Inland Regional Center on December 2, 2015 in San Bernardino, California. Police continue to search for suspects in the shooting that left at least 14 people dead and another 17 injured. (Photo by Sean M. Haffey/Getty Images)
SAN BERNARDINO, CA - DECEMBER 02: A California Highway Patrol officer stands with his weapon as authorities pursued the suspects in a shooting that occurred at the Inland Regional Center on December 2, 2015 in San Bernardino, California. Police continue to search for suspects in the shooting that left at least 14 people dead and another 17 injured. (Photo by Sean M. Haffey/Getty Images)
SAN BERNARDINO, CA - DECEMBER 02: A San Bernadino Sheriff helicopter flys above a neighborhood as authorities pursue suspects of the shooting at the Inland Regional Center on December 2, 2015 in San Bernardino, California. Police continue to search for suspects in the shooting that left at least 14 people dead and another 17 injured. (Photo by Sean M. Haffey/Getty Images)
SAN BERNARDINO, CA - DECEMBER 2: Officers swarm San bernardino Ave at Richardson Street near where suspects were shot in a black SUV December 2, 2015 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for suspects still at large. (Photo by Irfan Khan/Los Angeles Times via Getty Images)
Law enforcement officials with armored vehicles search an area near where police stopped a suspect SUV in San Bernardino, Calif., Wednesday, Dec. 2, 2015. The search followed a military-style attack that killed multiple people and wounded others at a California center that serves people with developmental disabilities, authorities said. (AP Photo/Chris Carlson)
Armored vehicles surround an SUV following a shootout in San Bernardino, Calif., Wednesday, Dec. 2, 2015. The scene followed a military-style attack that killed multiple people and wounded others at a California center that serves people with developmental disabilities, authorities said. (KNBC via AP) TV OUT
SAN BERNARDINO, CA - DECEMBER 2: Ambulances leave the scene of a mass shooting at the Inland Regional Center on December 2, 2105 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for up to three suspects who are still at-large. (Photo by Gina Ferazzi / Los Angeles Times via Getty Images)
SAN BERNARDINO, CA - DECEMBER 2: Police draw guns on San Bernardino Avenue while chasing suspects in an SUV December 2, 2015 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for suspects still at large. (Photo by Francine Orr/Los Angeles Times via Getty Images)
SAN BERNARDINO, CA - DECEMBER 2: Police draw guns on San Bernardino Avenue while chasing suspects in an SUV December 2, 2015 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for suspects still at large. (Photo by Francine Orr/Los Angeles Times via Getty Images)
SAN BERNARDINO, CA - DECEMBER 2: Police and emergency vehicles line Waterman Avenue in front of the Inland Regional Center in San Bernardino, scene of a mass shooting on December 2, 2105 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for up to three suspects who are still at large. (Photo by Luis Sinco/Los Angeles Times via Getty Images)
SAN BERNARDINO, CA - DECEMBER 2: Police and emergency vehicles line Waterman Avenue in front of the Inland Regional Center in San Bernardino, scene of a mass shooting on December 2, 2105 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for up to three suspects who are still at large. (Photo by Luis Sinco/Los Angeles Times via Getty Images)
Police at the scene of a shooting on December 2, 2015 in San Bernardino, California. One or more gunman opened fire inside a building in San Bernardino in California, with reports of 20 victims at a center that provides services for the disabled. Police were still hunting for the shooter, saying one to three possible suspects were involved. Heavily armed SWAT teams, firefighters and ambulances swarmed the scene, located about an hour east of Los Angeles, as police warned residents away. AFP PHOTO / FREDERIC J. BROWN / AFP / FREDERIC J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)
SAN BERNARDINO, CA - DECEMBER 02: Members of the FBI Joint Terrorism Task Force stand outside of a press conference regarding the shooting that occurred at the Inland Regional Center on December 2, 2015 in San Bernardino, California. Multiple fatalities were reported as police search for up to three suspects who are still at large. (Photo by Sean M. Haffey/Getty Images)
SAN BERNARDINO, CA - DECEMBER 02: Ambulances pull out of a staging area near the Inland Regional Center where a shooting occurred earlier in the day on December 2, 2015 in San Bernardino, California. Multiple fatalities were reported as police search for up to three suspects who are still at large. (Photo by Sean M. Haffey/Getty Images)
A heavily armed officer sets up a perimeter near the site of a shooting that took place on December 2, 2015 in San Bernardino, California. One or more gunman opened fire inside a building in San Bernardino in California, with reports of 20 victims at a center that provides services for the disabled. Police were still hunting for the shooter, saying one to three possible suspects were involved. Heavily armed SWAT teams, firefighters and ambulances swarmed the scene, located about an hour east of Los Angeles, as police warned residents away. AFP PHOTO / FREDERIC J. BROWN / AFP / FREDERIC J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)
SAN BERNARDINO, CA - DECEMBER 2: San Bernardino County Sheriffs deputies respond to a mass shooting at the Inland Regional Center December 2, 2015 in San Bernardino, California. Multiple fatalities were reported as police search for up to three suspects who are still at large. (Photo by David McNew/Getty Images)
SAN BERNARDINO, CA - DECEMBER 2: A San Bernardino County Sheriffs Department investigator responds to a mass shooting at the Inland Regional Center December 2, 2015 in San Bernardino, California. Multiple fatalities were reported as police search for up to three suspects who are still at large. (Photo by David McNew/Getty Images)
SAN BERNARDINO, CA - DECEMBER 2: Employees and other people are evacuated by bus from the site of a mass shooting at the Inland Regional Center December 2, 2015 in San Bernardino, California. Multiple fatalities were reported as police search for up to three suspects who are still at large. (Photo by David McNew/Getty Images)
Police escort civilians away from the 1300 block of S. Waterman Street near the site of a shooting took place on December 2, 2015 in San Bernardino, California. One or more gunman opened fire inside a building in San Bernardino in California, with reports of 20 victims at a center that provides services for the disabled. Police were still hunting for the shooter, saying one to three possible suspects were involved. Heavily armed SWAT teams, firefighters and ambulances swarmed the scene, located about an hour east of Los Angeles, as police warned residents away. AFP PHOTO / FREDERIC J. BROWN / AFP / FREDERIC J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)
Police escort civilians away from the 1300 block of S. Waterman Street near the site of a shooting took place on December 2, 2015 in San Bernardino, California. One or more gunman opened fire inside a building in San Bernardino in California, with reports of 20 victims at a center that provides services for the disabled. Police were still hunting for the shooter, saying one to three possible suspects were involved. Heavily armed SWAT teams, firefighters and ambulances swarmed the scene, located about an hour east of Los Angeles, as police warned residents away. AFP PHOTO / FREDERIC J. BROWN / AFP / FREDERIC J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)
Armed Sheriff's department personel man a roadblock at Waterman Street near the site of a shooting took place on December 2, 2015 in San Bernardino, California. One or more gunman opened fire inside a building in San Bernardino in California, with reports of 20 victims at a center that provides services for the disabled. Police were still hunting for the shooter, saying one to three possible suspects were involved. Heavily armed SWAT teams, firefighters and ambulances swarmed the scene, located about an hour east of Los Angeles, as police warned residents away. AFP PHOTO / FREDERIC J. BROWN / AFP / FREDERIC J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)
A swat team arrives at the scene of a shooting in San Bernardino, Calif. on Wednesday, Dec. 2, 2015. Police responded to reports of an active shooter at a social services facility. (Doug Saunders/Los Angeles News Group via AP) 
SAN BERNARDINO, CA - DECEMBER 2: Police and fire personnel secure the scene where a mass shooting occurred at the Inland Regional Center on December 2, 2105 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for up to three suspects who are still at large. (Photo by Gina Ferazzi / Los Angeles Times via Getty Images)
SAN BERNARDINO, CA - DECEMBER 2: San Bernardino police offices in SWAT gear secure the scene where a mass shooting occurred at the Inland Regional Center on December 2, 2105 in San Bernardino, California. Multiple fatalities and injuries were reported as police search for up to three suspects who are still at large. (Photo by Gina Ferazzi / Los Angeles Times via Getty Images)
A crowd gathers behind police line near the scene of a shooting on December 2, 2015 in San Bernardino, California. One or more gunman opened fire inside a building in San Bernardino in California, with reports of 20 victims at a center that provides services for the disabled. Police were still hunting for the shooter, saying one to three possible suspects were involved. Heavily armed SWAT teams, firefighters and ambulances swarmed the scene, located about an hour east of Los Angeles, as police warned residents away. AFP PHOTO / FREDERIC J. BROWN / AFP / FREDERIC J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)
Photo courtesy: AP
Photo courtesy: AP

A couple embraces following a shooting that killed multiple people at a social services facility, Wednesday, Dec. 2, 2015, in San Bernardino, Calif. (David Bauman/The Press-Enterprise via AP)

People are evacuated by law enforcement agencies from the Inland Regional Center the scene of a shooting in San Bernardino, Calif. on Wednesday, Dec. 2, 2015. Police in San Bernardino, California, were responding to reports of an active shooter at a social services facility. There were reports of multiple victims, Lt. Rich Lawhead said Wednesday. (Doug Saunders/Los Angeles News Group via AP)
A first responder attends to a person outside a Southern California social services center in San Bernardino, where authorities said multiple people were shot Wednesday, Dec. 2, 2015. (KNBC via AP)
People are evacuated by law enforcement agencies from the Inland Regional Center the scene of a shooting in San Bernardino, Calif. on Wednesday, Dec. 2, 2015. Police in San Bernardino, California, were responding to reports of an active shooter at a social services facility. There were reports of multiple victims, Lt. Rich Lawhead said Wednesday. (Doug Saunders/Los Angeles News Group via AP)
First responders attend to people outside a Southern California social services center in San Bernardino, where one or more gunmen opened fire, shooting multiple people on Wednesday, Dec. 2, 2015. (KNBC via AP)

First responders gather outside a Southern California social services center in San Bernardino, Calif., where authorities said multiple people were shot Wednesday, Dec. 2, 2015. (KTTV via AP)

A woman holds her arm as first responders attend to people outside a Southern California social services center in San Bernardino, Calif., where one or more gunmen opened fire, shooting multiple people on Wednesday, Dec. 2, 2015. (KNBC via AP) 
This aerial view shows a Southern California social services center in San Bernardino, Calif., where authorities said multiple people were shot Wednesday, Dec. 2, 2015. (KTTV via AP)
In this aerial view, first responders gather on a nearby street corner, lower left, outside a Southern California social services center, upper right, in San Bernardino, Calif., where authorities said multiple people were shot Wednesday, Dec. 2, 2015. (KTTV via AP)
First responders gather on a nearby street corner as victims are treated outside a Southern California social services center in San Bernardino, Calif., where authorities said multiple people were shot Wednesday, Dec. 2, 2015. (KTTV via AP)
Law enforcement officials walk with weapons drawn outside a Southern California social services center in San Bernardino, Calif., where authorities said multiple people were shot Wednesday, Dec. 2, 2015. (KTTV via AP)
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The FBI is investigating the massacre as a terrorist attack that, if proved, would be the deadliest by Islamic extremists on American soil since Sept. 11, 2001.

The woman pledged allegiance to IS and its leader in a Facebook post, according to U.S. official who was not authorized to discuss the case publicly and spoke on condition of anonymity. A Facebook official said the post came about the time the couple stormed the San Bernardino social service center.

Watch more coverage:

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