Sayfullo Saipov
Sayfullo SaipovReuters

Sayfullo Saipov, the terrorist who carried out Tuesday's attack in Manhattan in which eight people were killed, was charged on Wednesday with federal terrorism offenses, according to a document from the U.S. Attorney for the Southern District of New York.

Saipov, a 29-year-old Uzbek national who was living in New Jersey, is charged with providing material support to the Islamic State (ISIS) and violence and destruction of motor vehicles, according to CNN.

A criminal complaint filed against him said he confessed to authorities while in custody that he began planning the attack a year ago, reported Reuters.

The 10-page complaint said Saipov told investigators he was inspired by ISIS videos he had watched on his cellphone, chose Halloween for the attack because he believed more people would be on the streets, and had originally planned to strike the Brooklyn Bridge as well as the bike path.

The complaint also said Saipov had requested permission to display Islamic State’s flag in his hospital room and said he felt good about what he had done.

Meanwhile, the FBI is seeking the public's assistance with information about an Uzbekistan national in connection with the attack, according to an FBI poster released Wednesday.

The second suspect in question has been identified as Mukhammadzoir Kadirov, 32.

Earlier on Wednesday, NYPD deputy commissioner for intelligence and counterterrorism John Miller said that Saipov had planned the attack for weeks and carried out the killings "in the name of ISIS."

Authorities say Saipov drove a rented truck onto a well-trafficked bike path just blocks from the World Trade Center on Tuesday afternoon, killing eight and injuring more than a dozen before crashing into a school bus. He then left the vehicle brandishing imitation firearms and was shot by police, survived and was taken into custody.

A note written in Arabic praising ISIS was found inside the truck used by Saipov to commit the ramming attack, an NYPD official told NBC News. The note read: "ISIS lives forever."

Investigators who came to interview the terrorist reported that he was rejoicing at having murdered many innocent people.