The Uzbek who killed eight people in New York acted in the name of the Islamic State group, police confirmed Wednesday, as the US president vowed to scrap the visa program that allowed him to enter the country.
Tuesday's attack, which mowed down pedestrians and cyclists at high speed on Lower Manhattan's West Side, was the deadliest attack blamed on terrorism in America's financial capital since the September 11, 2001 hijackings.
While 29-year-old suspect Sayfullo Saipov had not previously been the subject of an FBI investigation, police confirmed he had planned the attack for weeks.
Saipov, who moved to America legally in March 2010, rented a pickup truck in New Jersey without suspicion, before driving into New York, mounting a bike path and unleashing mayhem as children and their parents prepared to celebrate Halloween.
Five of the dead were Argentines, visiting for a school reunion. A Belgian woman was also killed. Of 12 injured, nine remain in hospital -- four in a critical but stable condition. One Argentine, a German and three Belgians, were among the injured.
The suspect was shot in the abdomen by a police officer after he crashed into a school bus and exited his truck, brandishing paintball and pellet guns. He has been interviewed in hospital and remains in custody, police said.
"He did this in the name of ISIS," John Miller, the head of New York police intelligence and counter-terrorism, told a news conference.
"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," Miller added.
Vehicle rammings have been a frequent tactic deployed by IS sympathizers in the West, including in Barcelona, London, Stockholm and in Nice, where a Tunisian suicide truck bomber killed 86 people on Bastille Day last year.
Police said it was too early to determine when Saipov may have become radicalized, but New York Governor Andrew Cuomo said it happened after he moved to the United States. He is not a US citizen but a legal permanent resident.
Trump, confronting the worst jihadist-inspired attack of his 10 months in office, denounced Saipov as an "animal" and charged that he had been a point of contact for up to 23 immigrants or would-be immigrants, quipping that he "would certainly consider" sending him to Guantanamo Bay.
The Republican president said that he was "starting the process of terminating" the popular green card lottery, which he said had enabled Saipov to enter the country.
"We have to do what's right to protect our citizens," the Republican president told reporters. "We will get rid of this lottery program as soon as possible."
The 1990 program awards US permanent resident visas to around 50,000 applicants around the world each year, opening the door as well for members of their wider families to follow them, so-called chain migration.
Trump has already slashed the country's annual refugee intake by more than 50 percent, tightened visa issuance around the world and attempted to ban travelers from 11 countries, most of them with Muslim-majority populations, but not Uzbekistan.
"We also have to come up with punishment that's far quicker and far greater than the punishment these animals are getting right now," the president said.
Saipov lived in Florida and Ohio, before moving to Paterson, a former industrial hub in New Jersey about 20 miles (30 kilometers) northeast of New York, where he lived with his wife and three children. The truck was rented in New Jersey.
Neighbors in the working-class, immigrant community reacted with shock and horror on Wednesday, saying that they knew little about the man who kept to himself.
"It's a very quiet neighborhood. We leave our doors unlocked. We thought we were pretty safe, but to know that someone like that lives down the street is scary," said Kimberly Perez, 20, who lives across the street.
In New York, leaders vowed that the annual marathon would go ahead as planned on Sunday. Police said the event, which attracts more than 50,000 runners and 2.5 million spectators, would be the most protected ever.
"We will not be cowed, we will not be thrown off by anything," said Mayor Bill de Blasio.
While officials say preliminary evidence suggests Saipov acted alone and was not part of a wider plot, Cuomo has drastically stepped up security at airports, tunnels and Penn Station, which he called the busiest rail hub in the hemisphere.
Uzbekistan, a majority Muslim country that borders Afghanistan and formerly part of the Soviet Union, is a landlocked country racked with poverty, corruption and a stifling authoritarian regime.
In March 2015, two Uzbeks and a Kazakh living in New York were arrested on charges of supporting IS. One of them, who threatened former president Barack Obama, was sentenced to 15 years in prison last week.