Report: FBI and DHS assessment warned of lone offender threat months before Las Vegas shooting

The Federal Bureau of Investigation and Department of Homeland Security warned of the threat of a potential lone offender targeting mass gatherings just nine months before a Las Vegas gunman left 59 dead and hundreds more injured on Sunday night.

According to Foreign Policy, the FBI and DHS published the "Joint Special Event Threat Assesssment" in December 2016, which outlined the threat with targets including music venues in Las Vegas. The document obtained by Foreign Policy is unclassified and reveals that last year's New Year’s Eve celebrations along the Las Vegas Strip were of particular concern. 

"Unaffiliated lone offenders and [homegrown violent extremists] are of particular concern," so reads the document, "due to their ability to remain undetected until operational; their willingness to attack civilians and soft targets; their ability to inflict significant casualties with weapons that do not require specialized knowledge, access, or training; and their unpredictability, as witnessed in the Orlando, Florida and San Bernardino, California terrorist attacks."

RELATED: What we know about the Las Vegas shooter

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What we know about Las Vegas shooting suspect Stephen Paddock
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What we know about Las Vegas shooting suspect Stephen Paddock
Stephen Paddock, 64, allegedly opened fire from the Mandalay Bay Resort and Casino on the Route 91 Harvest country music festival, leaving at least 59 people dead and hundreds injured.

(Social media/Handout via REUTERS)

He reportedly used a hammer-like tool to break out two windows at the Mandalay Bay Resort and Casino.

(Photo by David Becker/Getty Images)

Stephen Paddock was reportedly a high-stakes gambler that lived in a retirement community in Mesquite, Nevada.

(REUTERS/Las Vegas Sun/Steve Marcus)

His father was Benjamin Hoskins Paddock, a bank robber and former FBI Most Wanted Fugitive.

(FBI/Handout via REUTERS)

Paddock killed himself before authorities breached his hotel room and investigators say he acted alone.

(REUTERS/Las Vegas Sun/Steve Marcus)

Paddock's girlfriend, Marilou Danley, was in the Philippines at the time of the shooting but he reportedly used her identification to check in at the Mandalay Bay hotel.

(Las Vegas Metropolitan Police Department/Handout via REUTERS)

Stephen Paddock lived in this home in Melbourne, Florida from 2013 to 2015.

(Joe Burbank/Orlando Sentinel/TNS via Getty Images)

Police said Paddock had no criminal record.

(Photo by David Becker/Getty Images)

NBC News reported that Paddock made several large gambling transactions in recent weeks, but that it wasn't clear if they were wins or losses.

(Photo by David Becker/Getty Images)

Paddock reportedly purchased firearms at  Guns & Guitars, a gun shop in Mesquite, Nevada. 

(Photo by Gabe Ginsberg/Getty Images)

Paddock's brother, Eric, said his sibling belonged to no political or religious organizations, and had no history of mental illness.

 (Photo by Marcus Yam/Los Angeles Times via Getty Images)

Paddock's brother described him as a "wealthy guy" and said he liked to play video poker and go on cruises.

(Photo by Gabe Ginsberg/Getty Images)

He worked as an accountant and had real estate investments, according to the Washington Post. 

(Photo by Drew Angerer/Getty Images)

Paddock had his pilot license and owned at least one plane, according to Reuters.

(REUTERS/Lucy Nicholson)
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Before Las Vegas, mass shootings around the world -- including in Orlando at Pule Nightclub -- have repeatedly targetted crowds out at concerts, enjoying nightlife or in open-era venues. The DHS and FBI joint assessment mirrors one often conducted before large U.S. events, and similar breakdowns were recently conducted in lead-up to the Macy's Thanksgiving Day Parade and U.N. General Assembly in New York.

It is important to note that the report, at the time, had "no information to indicate a specific, credible threat to or associated with the America’s Party New Year’s Eve celebration on the Las Vegas Strip and Downtown Las Vegas."

The threat assessment specifically instructed local law enforcement to watch for key behavior indicators, but FP has not made those specific signs public at the request of the FBI.

64-year-old Stephen Paddock fired shots on a Las Vegas country music festival on Sunday from a 32nd-floor window in the Mandalay Bay hotel on Sunday night, before eventually killing himself. The assault lasted several minutes, causing mass panic as thousands fled the scene. Officials are still searching for the gunman's clear motive in perpetrating the deadliest mass shooting in U.S. history.

RELATED: A look at the devastating Las Vegas shooting

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Route 91 Harvest country music festival shooting in Las Vegas
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Route 91 Harvest country music festival shooting in Las Vegas
LAS VEGAS, NV - OCTOBER 02: A cowboy hat lays in the street after shots were fired near a country music festival on October 1, 2017 in Las Vegas, Nevada. A gunman has opened fire on a music festival in Las Vegas, leaving at least 20 people dead and more than 100 injured. Police have confirmed that one suspect has been shot. The investigation is ongoing. (Photo by David Becker/Getty Images)
LAS VEGAS, NV - OCTOBER 01: ( A person lies on the ground covered with blood at the Route 91 Harvest country music festival after apparent gun fire was heard on October 1, 2017 in Las Vegas, Nevada. There are reports of an active shooter around the Mandalay Bay Resort and Casino. (Photo by David Becker/Getty Images)
LAS VEGAS, NV - OCTOBER 01 People run from the Route 91 Harvest country music festival after apparent gun fire was heard on October 1, 2017 in Las Vegas, Nevada. There are reports of an active shooter around the Mandalay Bay Resort and Casino. (Photo by David Becker/Getty Images)
LAS VEGAS, NV - OCTOBER 01:  A person lies on the ground at the Route 91 Harvest country music festival after apparent gun fire was heard on October 1, 2017 in Las Vegas, Nevada. There are reports of an active shooter around the Mandalay Bay Resort and Casino. (Photo by David Becker/Getty Images)
LAS VEGAS, NV - OCTOBER 01: People dive for cover at Route 91 Harvest country music festival after apparent gun fire was heard on October 1, 2017 in Las Vegas, Nevada. There are reports of an active shooter around the Mandalay Bay Resort and Casino. (Photo by David Becker/Getty Images)
LAS VEGAS, NV - OCTOBER 01: People tend to the wounded outside the festival ground after an apparent shooting on October 1, 2017 in Las Vegas, Nevada. There are reports of an active shooter around the Mandalay Bay Resort and Casino. (Photo by David Becker/Getty Images)
LAS VEGAS, NV - OCTOBER 01: People run from the Route 91 Harvest country music festival after apparent gun fire was hear on October 1, 2017 in Las Vegas, Nevada. A gunman has opened fire on a music festival in Las Vegas, leaving at least 20 people dead and more than 100 injured. Police have confirmed that one suspect has been shot. The investigation is ongoing. (Photo by David Becker/Getty Images)
LAS VEGAS, NV - OCTOBER 01: People take cover at the Route 91 Harvest country music festival after apparent gun fire was heard on October 1, 2017 in Las Vegas, Nevada. There are reports of an active shooter around the Mandalay Bay Resort and Casino. (Photo by David Becker/Getty Images)
LAS VEGAS, NV - OCTOBER 01: A person runs from the Route 91 Harvest country music festival after apparent gun fire was heard on October 1, 2017 in Las Vegas, Nevada. There are reports of an active shooter around the Mandalay Bay Resort and Casino. (Photo by David Becker/Getty Images)
LAS VEGAS, NV - OCTOBER 01: People scramble for shelter at the Route 91 Harvest country music festival after apparent gun fire was heard on October 1, 2017 in Las Vegas, Nevada. A gunman has opened fire on a music festival in Las Vegas, leaving at least 20 people dead and more than 100 injured. Police have confirmed that one suspect has been shot. The investigation is ongoing. (Photo by David Becker/Getty Images)
LAS VEGAS, NV - OCTOBER 01: A man in a wheelchair is taken away from the Route 91 Harvest country music festival after apparent gun fire was heard on October 1, 2017 in Las Vegas, Nevada. There are reports of an active shooter around the Mandalay Bay Resort and Casino. (Photo by David Becker/Getty Images)
LAS VEGAS, NV - OCTOBER 02: Las Vegas Metropolitan Police officers run down Tropicana Ave. near Las Vegas Boulevard after a mass shooting at a country music festival nearby on October 2, 2017 in Las Vegas, Nevada. A gunman has opened fire on a music festival in Las Vegas, killing over 20 people. Police have confirmed that one suspect has been shot dead. The investigation is ongoing. (Photo by Ethan Miller/Getty Images)
LAS VEGAS, NV - OCTOBER 01: A man lays on top of a woman as others flee the Route 91 Harvest country music festival grounds after a active shooter was reported on October 1, 2017 in Las Vegas, Nevada. A gunman has opened fire on a music festival in Las Vegas, leaving at least 2 people dead. Police have confirmed that one suspect has been shot. The investigation is ongoing. (Photo by David Becker/Getty Images)
LAS VEGAS, NV - OCTOBER 02: People hug and cry outside the Thomas & Mack Center after a mass shooting at the Route 91 Harvest country music festival on October 2, 2017 in Las Vegas, Nevada. A gunman, identified as Stephen Paddock, 64, of Mesquite, Nevada, opened fire from the Mandalay Bay Resort and Casino on the music festival, leaving at least 50 people dead and hundreds injured. Police have confirmed that one suspect has been shot. The investigation is ongoing. (Photo by Ethan Miller/Getty Images)
LAS VEGAS, NV - OCTOBER 02: UNLV student Ajay Narang (L) and a Las Vegas Metropolitan Police Department officer use Narang's skateboard to help deliver bottled water to people at the Thomas & Mack Center after a mass shooting at a country music festival on October 2, 2017 in Las Vegas, Nevada. People who could not go to hotel-casinos that were closed after the shooting are temporarily staying at the center. A gunman, identified as Stephen Paddock, 64, of Mesquite, Nevada, opened fire from the Mandalay Bay Resort and Casino on the music festival, leaving at least 50 people dead and hundreds injured. Police have confirmed that one suspect has been shot. The investigation is ongoing. (Photo by Ethan Miller/Getty Images)
LAS VEGAS, NV - OCTOBER 02: A Las Vegas Metropolitan Police Department officer helps deliver blankets and food to people at the Thomas & Mack Center after a mass shooting at a country music festival on October 2, 2017 in Las Vegas, Nevada. People who could not go to hotel-casinos that were closed after the shooting are temporarily staying at the center. A gunman, identified as Stephen Paddock, 64, of Mesquite, Nevada, opened fire from the Mandalay Bay Resort and Casino on the music festival, leaving at least 50 people dead and hundreds injured. Police have confirmed that one suspect has been shot. The investigation is ongoing. (Photo by Ethan Miller/Getty Images)
LAS VEGAS, NV - OCTOBER 02: People are directed to rides outside the Thomas & Mack Center after a mass shooting at a country music festival on October 2, 2017 in Las Vegas, Nevada. People who could not go to hotel-casinos that were closed after the shooting are temporarily staying at the center. The gunman, identified as Stephen Paddock, 64, of Mesquite, Nevada, opened fire from the Mandalay Bay Resort and Casino on the music festival, leaving at least 50 people dead and hundreds injured. Police have confirmed that one suspect has been shot. The investigation is ongoing. (Photo by Ethan Miller/Getty Images)
LAS VEGAS, NV - OCTOBER 02: Concert-goers wait for a ride outside the Thomas & Mack Center after a mass shooting at a country music festival on October 2, 2017 in Las Vegas, Nevada. People who could not go to hotel-casinos that were closed after the shooting temporarily stayed at the center. The gunman, identified as Stephen Paddock, 64, of Mesquite, Nevada, opened fire from the Mandalay Bay Resort and Casino on the music festival, leaving at least 50 people dead and hundreds injured. Police have confirmed that one suspect has been shot. The investigation is ongoing. (Photo by Ethan Miller/Getty Images)
LAS VEGAS, NV - OCTOBER 02: A Las Vegas Metropolitan Police Department officer helps deliver bottled water to people at the Thomas & Mack Center after a mass shooting at a country music festival on October 2, 2017 in Las Vegas, Nevada. People who could not go to hotel-casinos that were closed after the shooting are temporarily staying at the center and residents are donating supplies. The gunman, identified as Stephen Paddock, 64, of Mesquite, Nevada, opened fire from the Mandalay Bay Resort and Casino on the music festival, leaving at least 50 people dead and hundreds injured. Police have confirmed that one suspect has been shot. The investigation is ongoing. (Photo by Ethan Miller/Getty Images)
LAS VEGAS, NV - OCTOBER 02: Concert-goers wait for a ride outside the Thomas & Mack Center after a mass shooting at a country music festival on October 2, 2017 in Las Vegas, Nevada. People who could not go to hotel-casinos that were closed after the shooting temporarily stayed at the center. The gunman, identified as Stephen Paddock, 64, of Mesquite, Nevada, opened fire from the Mandalay Bay Resort and Casino on the music festival, leaving at least 50 people dead and hundreds injured. Police have confirmed that one suspect has been shot. The investigation is ongoing. (Photo by Ethan Miller/Getty Images)
LAS VEGAS, NV - OCTOBER 02: A Las Vegas Metropolitan Police Department officer helps deliver bottled water to people at the Thomas & Mack Center after a mass shooting at a country music festival on October 2, 2017 in Las Vegas, Nevada. People who could not go to hotel-casinos that were closed after the shooting are temporarily staying at the center and residents are donating supplies. The gunman, identified as Stephen Paddock, 64, of Mesquite, Nevada, opened fire from the Mandalay Bay Resort and Casino on the music festival, leaving at least 50 people dead and hundreds injured. Police have confirmed that one suspect has been shot. The investigation is ongoing. (Photo by Ethan Miller/Getty Images)
A pair of cowboy boots is shown in the street outside the concert venue after a mass shooting at a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. October 1, 2017. REUTERS/Las Vegas Sun/Steve Marcus
LAS VEGAS, NV - OCTOBER 02: Police officers stop a man who drove down Tropicana Ave. near Las Vegas Boulevard and Tropicana Ave, which had been closed after a mass shooting at a country music festival that left at least 2 people dead nearby on October 2, 2017 in Las Vegas, Nevada. The man was released. (Photo by Ethan Miller/Getty Images)
Metro Police officers pass by the front of the Tropicana hotel-casino after a mass shooting at a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. October 1, 2017. REUTERS/Las Vegas Sun/Steve Marcus
LAS VEGAS, NV - OCTOBER 02: A Las Vegas Metropolitan Police officer stands in the intersection of Las Vegas Boulevard and Tropicana Ave. after a mass shooting at a country music festival nearby on October 2, 2017 in Las Vegas, Nevada. A gunman has opened fire on a music festival in Las Vegas, killing over 20 people. Police have confirmed that one suspect has been shot dead. The investigation is ongoing. (Photo by Ethan Miller/Getty Images)
Las Vegas Metro Police officers work near the concert venue after a mass shooting at a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. October 1, 2017. REUTERS/Las Vegas Sun/Steve Marcus
A body is covered with a sheet in the intersection of Tropicana Avenue and Las Vegas Boulevard South after a mass shooting at a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. October 1, 2017. REUTERS/Las Vegas Sun/Steve Marcus
Las Vegas Metro Police and medical workers stage in the intersection of Tropicana Avenue and Las Vegas Boulevard South after a mass shooting at a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. October 1, 2017. REUTERS/Las Vegas Sun/Steve Marcus TPX IMAGES OF THE DAY
An ambulance leaves the concert venue after a mass shooting at a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. October 1, 2017. REUTERS/Las Vegas Sun/Steve Marcus
An ambulance heads to a hospital after a mass shooting at a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. October 1, 2017. REUTERS/Las Vegas Sun/Steve Marcus
Medical workers stage in the intersection of Tropicana Avenue and Las Vegas Boulevard South after a mass shooting at a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. early October 2, 2017. REUTERS/Las Vegas Sun/Steve Marcus
Las Vegas Metro Police officers gather near the intersection of Tropicana Avenue and Las Vegas Boulevard South after a mass shooting at a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. early October 2, 2017. REUTERS/Las Vegas Sun/Steve Marcus
Las Vegas Metro Police officers confer near a staging area in the intersection of Tropicana Avenue and Las Vegas Boulevard South after a mass shooting at a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. early October 2, 2017. REUTERS/Las Vegas Sun/Steve Marcus
Las Vegas Metro Police and medical workers stage in the intersection of Tropicana Avenue and Las Vegas Boulevard South after a mass shooting at a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. October 1, 2017. REUTERS/Las Vegas Sun/Steve Marcus
Las Vegas Metro Police officer stands by at a staging area in the intersection of Tropicana Avenue and Las Vegas Boulevard South after a mass shooting at a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. early October 2, 2017. REUTERS/Las Vegas Sun/Steve Marcus
Las Vegas Metro Police and medical workers stage in the intersection of Tropicana Avenue and Las Vegas Boulevard South after a mass shooting at a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. October 1, 2017. REUTERS/Las Vegas Sun/Steve Marcus
 Police form a perimeter around the road leading to the Mandalay Hotel (background) after a gunman killed at least 50 people and wounded more than 200 others when he opened fire on a country music concert in Las Vegas, Nevada on October 2, 2017. Police said the gunman, a 64-year-old local resident named as Stephen Paddock, had been killed after a SWAT team responded to reports of multiple gunfire from the 32nd floor of the Mandalay Bay, a hotel-casino next to the concert venue. / AFP PHOTO / Mark RALSTON (Photo credit should read MARK RALSTON/AFP/Getty Images)
Metro Police officers speak with a man near the concert site on October 2, 2017, after a mass shooting during a music festival on the Las Vegas Strip in Las Vegas, Nevada, U.S. REUTERS/Las Vegas Sun/Steve Marcus
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