The 29-year-old terror suspect, Sayfullo Habibullaevic Saipov, who deliberately drove into bicyclists and pedestrians on a bike path in Lower Manhattan on 31 October, killing at least eight people and injuring many, left a note behind in the rental truck, pledging his allegiance to the Islamic State of Iraq and Syriac (ISIS).
Hours after the attack, the U.S. President Donald Trump said that the United States must not let the ISIS "return to or enter" the country.
"We must not allow ISIS to return, or enter, our country after defeating them in the Middle East and elsewhere. Enough!" Trump tweeted.
Trump's tweets came after the New York City Mayor Bill de Blasio called the incident "an act of terror."
"Based on information we have at this moment, this was an act of terror, and a particularly cowardly act of terror aimed at innocent civilians," Blasio said at a news conference.
According to the NBC News, the attacker was an Uzbek national who came to the U.S. in 2010 and has been living in Florida for the past seven years.
Meanwhile, a friend of the suspect who said he met Saipov five years ago when they both lived in Florida said, "he is no terrorist."
"He was a very happy guy," said Kobiljon Matkarov, who added that Saipov was married with kids and worked as a truck driver. "He liked the U.S."
A senior law enforcement official said that the Federal authorities were treating the incident as a terrorist attack.
"He jumped out of the truck with a pellet gun, yelled, 'Allahu Akbar,' and the First Precinct lit him up," a law enforcement official said.
Officials said it was the deadliest terrorist attack in New York City since 9/11.