The subway scenario -- straphangers being terrorized by roving shooters -- was fake. The response from NYPD officers and other rescuers Sunday couldn't have been more real.

NYPD officers in a department on edge since Nov. 13 attacks killed 130 and injured hundreds in Paris, flooded into a closed subway stop near Chinatown in lower Manhattan to simulate a real attack by two shooters -- one in a suicide vest.

After the simulated attack, which began in the predawn hours and ended shortly after 8 a.m., Police Commissioner William Bratton said it was designed to test coordination between the NYPD and the FDNY.

"Lessons learned here will certainly be quickly spread throughout the NYPD and fire department of New York City but also then through Homeland Security across the country," Bratton said. "These exercises are vitally important especially in light of all that's going on in the world at this time."

The elaborate dress rehearsal called for a scenario in which 30 people had been killed and 12 were injured. It was the first simulation to test two new units within the New York Police Department: the critical response command with more than 500 trained counterterrorism officers; and the 800-strong strategic response group.

This year's budget included money for more than 1,000 new officers, many of whom are expected to go into the new units.

The federal Department of Homeland Security used the exercise to test technologies including GoPro-like cameras worn by first responders and acoustic shot spotters designed to give police and firefighters information to coordinate response.

First responders participate in an active-shooter drill on Sunday, Nov....

First responders participate in an active-shooter drill on Sunday, Nov. 22, 2015, in and around a closed subway station near Chinatown in lower Manhattan. Credit: Charles Eckert

The first responders to go into the subway were transit officers.

"They go down and they move to the shooter -- that's our training -- and neutralize the threat," said James Waters, chief of the NYPD's counterterrorism unit. Then the police Emergency Service Unit, equipped with "long guns" and heavy vests, take over the operation and take out the shooters. Medical personnel then go into the scene with police protection.

As the drills ended, firefighters pulled "victims" away from the scene on yellow plastic sheets that slid across the sidewalk like snow sleds.

After the heavy show of NYPD might, Homeland Security Secretary Jeh Johnson said in a news conference that people should not be dissuaded from visiting New York City as holidays approach.

Johnson said copycat and lone-wolf attacks continue to be a concern but he reiterated what Bratton and other city officials have said since the Paris attacks -- there are no specific threats vowing similar carnage against New York City and people should go on with their lives.

"Terrorism cannot prevail if people refuse to be terrorized," Johnson said. "We encourage Americans as the holiday season approaches to continue to travel, associate, go to public events, go to public places."

The annual Thanksgiving parade will crawl south through the heart of the city, passing Times Square before ending at Herald Square. Both areas were included in a video released by ISIS last week that threatened more attacks. Bratton said the NYPD is prepared.

"It's going to be a great event," Bratton said during an interview after the drill on NBC's Meet the Press. "And it will be a safe and secure event."

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