A pickup driver killed eight people in New York on Tuesday by racing a truck down cyclists and pedestrians before striking a school bus in broad daylight
"This was an act of terror and a particularly cowardly act of terror aimed at innocent civilians, aimed at people going about their lives who had no idea what was about to hit them," said Mayor Bill de Blasio.
Law enforcement sources identified the perpetrator as Sayfullo Saipov, 29. He was arrested in Missouri on a traffic fine last year.
The Uzbek citizen living in Tampa, Florida had recently been staying in New Jersey, where the truck was rented, reports said.
The ride-hailing service Uber confirmed late Tuesday night that Saipov was one if its drivers. The company said he passed a background check and had been actively driving on the platform for more than six months. He has since been banned from the Uber app.
"We are horrified by this senseless act of violence," the company said in a statement. "Our hearts are with the victims and their families. We have reached out to law enforcement to provide our assistance."
President Donald Trump denounced him as "very sick" and a "deranged person."
Confronting what could be the most serious terror-related incident since taking power less than a year ago, the Republican commander-in-chief announced that he had ordered the Department of Homeland Security to step up his "extreme vetting program" on foreign travelers to the country.
The United States "must not" allow ISIS militants to "return, or enter" the country after being defeated overseas, Trump said on Twitter, albeit as New York officials declined to link the assailant to a specific group.
Police said he drove a rented Home Depot pickup down a bike and pedestrian lane, where tourists and New Yorkers were out enjoying brilliant fall sunshine, at 3:05 pm, before colliding with a school bus, wounding two adults and two children.
The suspect then exited the vehicle brandishing weapons that were subsequently identified as a paintball gun and pellet gun, before being shot in the abdomen by a police officer and taken into custody, police said.
Television footage showed the mangled wreckage of the pickup truck, bicycles crushed to smithereens and bodies wrapped in sheets and lying on the ground.
Eight people were killed, six of them men who died on the spot, and two others pronounced dead in hospital. Eleven other people were taken to hospital with serious but not life-threatening injuries, officials said.
Heavily-armed police fanned out across the city of 8.5 million. Security was stringent at airports, bridges, tunnels and mass transit systems, with bag searches at Manhattan's Grand Central transit hub and police stationed along a subway platform in Brooklyn.