New York: The New York terror attack suspect had been planning his deadly rampage for a "number of weeks", scouting out the best open spaces in Manhattan to mow down pedestrians and cyclists, authorities said on Thursday.
As Sayfullo Habibullaevic Saipov, 29, remained under police guard in hospital on Thursday, the FBI and NYPD intensified its hunt for clues to what led up to the attack, digging deeper into the life of a man who arrived in the US just six years ago.
In the New Jersey suburb of Paterson where the suspect lived with his wife and three children, investigators scoured his home on Wednesday and interviewed his wife, while in Uzbekistan, the focus turned to intelligence reports about militant factions in the Central Asian nation.
Saipov had been associated with social media accounts that contain ISIS-related material, a law enforcement official said on Wednesday.
CNN reported that an official said Saipov, who came to the US on a diversity visa, had been somewhat cooperative with the FBI who questioned him in the hospital overnight. Sources told CBS News that Saipov has been bragging about the attack and is unapologetic.
Law enforcement officials told ABC News in the US that the suspect was interviewed in 2015 by federal agents about possible ties to suspected terrorists, but the agents did not have enough evidence to open a case on him.
He had allegedly plotted the New York attack for weeks, and had previously hired a vehicle to do a dry run, ABC News reported. A source said he seemed "proud" of the attack.
Saipov was "radicalised domestically" in the US, New York governor Andrew Cuomo said Wednesday morning.
"The evidence shows - and again, it's only several hours, and the investigation is ongoing - but that after he came to the United States, he started to become informed about ISIS and radical Islamic tactics," Cuomo said.
"We have no evidence yet of associations or a continuing plot or associated plots, and our only evidence to date is that this was an isolated incident that he himself performed."
John Miller, NYPD deputy commissioner for intelligence and counter-terrorism, said Saipov had been planning "for a number of weeks" and appeared to closely follow instructions disseminated by Islamic State to followers.
"He appears to have followed, almost exactly to a 'T,' the instructions that ISIS has put out in its social media channels before with instructions to their followers on how to carry out such an attack," he said.
He said a handwritten Arabic note was found in the wreckage of the rented vehicle and the gist of its message "was that the Islamic State would endure forever".
Authorities say Saipov rented a ute from New Jersey and drove into Manhattan, careening down 17 blocks of a bike path at high speed along the Hudson River on Tuesday afternoon.
He turned an ordinary vehicle into a lethal weapon, running down locals and tourists before police officer Ryan Nash fired nine shots - at least one hitting him in the abdomen - and he was taken into custody.
His trail of terror left an almost kilometre-long path strewn with bodies, mangled bicycles, and personal items, including handbags and backpacks.
Among the eight people killed were five Argentines and a Belgian in what became New York's deadliest terrorist attack since September 11, 2001.
It also emerged that Saipov entered the US six years ago under a visa program to encourage immigration from under- represented nations, President Trump said on Wednesday.
Trump called on Congress to immediately end the Diversity Immigrant Visa Program, which issues up to 50,000 visas a year under the program using a lottery system.
"We need to get rid of the lottery program as soon as possible," Trump said before a Cabinet meeting at the White House.
Saipov, a bearded man of slim build, was captured on video running through traffic on Chambers Street.
A witness, Tawhid Kabir Xisan, said he saw a man running in the street carrying two guns.
"I heard five to six gunshots, and then when the gunshots was happening, I didn't see what happened on the road because I was scared," he said.
A spokesman for the FBI's New York office, Martin Feely, declined to comment on whether Saipov was known to the FBI.