James Waters, the head of the New York Police Department's Counterterrorism Bureau, believes a terrorist attack on American soil is bound to happen eventually. He says his job is to be ready for when that happens.
Waters told ABC "It's inevitable that there will be an attack or another attack in this country, but we are well-prepared to respond to that."
Waters is in charge of the city's Critical Response Command, the NYPD's standing unit of specially-trained counterterrorism officers. The unit is designed so at least 100 officers can respond to a threat at any time.
RELATED: See the most iconic images from 9/11
9/11/2001: 14 most iconic images of 9/11
9/11/2001: 14 most iconic images of 9/11
NEW YORK - SEPTEMBER 11, 2001: (FILE PHOTO) A fiery blasts rocks the south tower of the World Trade Center as the hijacked United Airlines Flight 175 from Boston crashes into the building September 11, 2001 in New York City. Almost two years after the September 11 attack on the World Trade Center, the New York Port Authority is releasing transcripts on August 28, 2003 of emergency calls made from inside the twin towers. (Photo by Spencer Platt/Getty Images)
Sarasota, UNITED STATES: TO GO WITH AFP STORY 'Americans mark 9/11 anniversary with new questions on vulnerability' - (FILES) US President George W. Bush has his early morning school reading event interupted by his Chief of Staff Andrew Card (L) shortly after news of the New York City airplane crashes was available in Sarasota, Florida 11 September 2001. AFP Photo Paul J. RICHARDS (Photo credit should read PAUL J. RICHARDS/AFP/Getty Images)
Americans mark 9/11 anniversary with new questions on vulnerability' - This 11 September 2001 file photo shows Marcy Borders covered in dust as she takes refuge in an office building after one of the World Trade Center towers collapsed in New York. Borders was caught outside on the street as the cloud of smoke and dust enveloped the area. The woman was caught outside on the street as the cloud of smoke and dust enveloped the area. AFP PHOTO/Stan HONDA (Photo credit should read STAN HONDA/AFP/Getty Images)
New York, UNITED STATES: TO GO WITH AFP STORY 'Americans mark 9/11 anniversary with new questions on vulnerability' - (FILES) The rubble of the World Trade Center smoulders following a terrorist attack 11 September 2001 in New York. Americans mark the fourth anniversary of the September 11, 2001 terror attacks Sunday nagged by new burning questions about their readiness to confront a major disaster after the debacle of Hurricane Katrina. AFP PHOTO/Alex Fuchs (Photo credit should read ALEX FUCHS/AFP/Getty Images)
394471 13: Firefighter Tony James cries while attending the funeral service for New York Fire Department Chaplain Rev. Mychal Judge, in front of the St. Francis of Assisi Church September 15, 2001 in New York City. Judge died while giving the last rites to a fireman in the collapse of the World Trade Center. The World Trade Center was destroyed after both the landmark towers were struck by two hijacked planes in an alleged terrorist attack on September 11. (Photo by Joe Raedle/Getty Images)
NEW YORK - SEPTEMBER 8: The 'Tribute in Light' memorial as seen from Bayonne, New Jersey, consists of two shafts of light to represent the World Trade Center Twin Towers, is tested before the fifth anniversary of 9/11 terrorist attacks September 8, 2006 in New York City. (Photo by Sylwia Kapuscinski/Getty Images)
NEW YORK- SEPTEMBER 3: A wax replica of Thomas Franklin's photograph from September 11, is seen at Madame Tussaud's wax museum September 3, 2002 in New York City. The replica is to be part of an exhibit at the museum called 'Hope: Humanity and Heroism.' (Photo by Spencer Platt/Getty Images)
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ABC News visited the unit ahead of the Fourth of July weekend to learn about precautions the city is taking. There's been no credible threats made to New York City or any other U.S. city over the holiday weekend, but the department is still in a heightened state of readiness.
As part of its operations, the NYPD monitors video from 9,000 surveillance cameras placed around the city. They also photograph 3 million license plate numbers from vehicles moving through the city every day; that data is kept on file for five years.
It's an extensive surveillance web and has raised privacy concerns from some New Yorkers. Waters told ABC the system is designed to give New Yorkers the same amount of privacy they can expect in public spaces while still keeping people safe.
New York City has plenty of experience with being singled out as a terrorism target. In April, a hoax "ISIS hit list" prompted the FBI to issue warnings to thousands of random New Yorkers named on the list.