New York: US president Donald Trump said the Uzbek immigrant accused of killing eight people when he drove a truck down a New York City bike path should get the death penalty.
The suspect, Sayfullo Saipov, told investigators he was inspired by watching Islamic State videos and began planning Tuesday's attack a year ago, according to a criminal complaint filed against him on Wednesday.
Saipov, 29, also said "he felt good about what he had done" and asked for permission to display the flag of the militant group Islamic State in his hospital room, the complaint said.
"NYC terrorist was happy as he asked to hang ISIS flag in his hospital room. He killed 8 people, badly injured 12. SHOULD GET DEATH PENALTY!" Trump tweeted late on Wednesday.
Saipov faces two charges, one of which carries the death penalty if the government chooses to seek it, Manhattan acting U.S attorney Joon Kim said.
The charges are one count of violence and destruction of motor vehicles causing the deaths of eight people and one count of providing material support and resources to a foreign terrorist organization - Islamic State, also known as ISIS.
The maximum penalty for the first is death; the maximum for the second life in prison, Kim said.
The charging document said Saipov waived his rights to remain silent, avoid self-incrimination and have an attorney present when he agreed to speak to investigators from his bed at Bellevue Hospital Center in Manhattan, where he was being treated after being shot by a police officer.
It said he was particularly motivated by a video where Abu Bakr al-Baghdadi - the leader of Islamic State - exhorted Muslims in the United States and elsewhere to support the group's cause.
Investigators found thousands of ISIS-related propaganda images and videos on Saipov's cellphone, the complaint said. Among them were video clips showing ISIS prisoners being beheaded, run over by a tank and shot in the face.
The Federal Bureau of Investigation said it had located another Uzbek man, Mukhammadzoir Kadirov, 32, wanted for questioning as a person of interest in the attack.
US law enforcement officials, speaking on condition of anonymity because the investigation was continuing, told Reuters that Saipov had been in contact with Kadirov and another person of interest in the investigation.
Assault deadliest since Sept 11, 2001
Tuesday's assault was the deadliest in New York City since the attack on Sept. 11, 2001, when hijackers crashed two jetliners into the World Trade Center, killing more than 2,600 people.
Five Argentine tourists, a Belgian, a New Yorker and a New Jersey man were killed in the attack.
Saipov, who lived in Paterson, New Jersey, allegedly used a pickup truck rented from a New Jersey Home Depot to run down pedestrians and cyclists along a 20-block stretch of the Manhattan bike path, before slamming into a school bus.
He got out of the truck shouting "Allahu Akbar" - Arabic for "God is greatest" - and brandishing what turned out to be a paint-ball gun and a pellet gun, authorities said, before a police officer shot him.
Seated in a wheelchair, Saipov appeared for a hearing in Manhattan federal court on Wednesday before magistrate judge Barbara Moses. Public defense attorney David Patton was appointed to represent him.
Saipov did not ask for bail and was remanded to federal custody. It was not immediately clear where he would be held.
Earlier in the day, Trump said he would consider sending Saipov to the military prison at the US naval base at Guantanamo Bay, Cuba. No detainee has been sent to the Guantanamo prison since 2008.
White House spokeswoman Sarah Sanders later told reporters that Trump considers Saipov an "enemy combatant," a designation that would curtail his legal rights. Trump called him "this animal" and lambasted the US justice system for terrorism suspects as "a joke" and "a laughingstock".
Kim said charging Saipov in civilian court would not necessarily prevent him from later being declared an enemy combatant.