Terror suspect Sayfullo Saipov spent weeks planning to conduct an attack in the name of the Islamic State group, police said Wednesday after eight people were killed in New York's worst attack since September 11, 2001.
Authorities say Saipov, an Uzbek immigrant who moved to America in 2010, used a rented pickup truck to mow down pedestrians and cyclists along a mile-long stretch of a bike path on Lower's Manhattan's West Side on Tuesday.
"Based on the investigation overnight, it appears that Mr Saipov had been planning this for a number of weeks," John Miller, deputy commissioner of the New York Police Department, told a news conference.
"He did this in the name of ISIS."
Miller said notes recovered at the scene show Saipov apparently had followed "almost exactly to a 'T' the instructions that ISIS has put out in its social media channels."
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New York State Governor Andrew Cuomo earlier told CNN that Saipov was radicalized domestically.
Police shot Saipov after the attack and he remains in the hospital.
Federal and local authorities quickly dug into Saipov's past after the attack, which occurred as children and their parents prepared to celebrate Halloween, but he was not previously known to counter-terrorism officials.
"Saipov has never been the subject of an NYPD intelligence bureau investigation, nor has he been the subject of an FBI investigation," Miller said.
Speaking at the same news conference, Mayor Bill de Blasio said the New York marathon would proceed as planned, albeit with heightened security measures.
"It will be an extraordinary event, as it always is," de Blasio said of the event involving more than 50,000 runners -- and 2.5 million spectators lining the streets to cheer them on.
The beefed-up security will feature more sand trucks parked to prevent vehicle attacks, extra police stationed on rooftops, and more anti-sniper units, among other steps, New York police chief Carlos Gomez said.
