The Uzbek immigrant, who crashed his truck into cyclists on Tuesday, has been charged by US prosecutors with causing the deaths of at least eight people in New York by mowing them down in a truck.
29-year-old Sayfullo Saipov is also accused of providing material support and resources to Islamic State (IS) group.
He was shot and injured by police at the scene of the attack, and received treatment in hospital.
Prosecutors say Mr Saipov spoke freely to them, waiving his right to avoid self-incrimination while in custody.
US President Donald Trump tweeted that he should receive the death penalty. The charges filed against Mr Saipov are federal, which means the government can override New York state’s ban on capital punishment.
Federal court papers allege:
1. Mr Saipov said the attack was planned two months ago
2. He said he had intentionally chosen Halloween so that the streets would be crowded
3. He wanted to display IS flags on the truck, but decided not to draw attention to himself
4. Authorities recovered 90 graphic and violent IS propaganda videos from his phones
5. He said he was inspired by them – in particular, one in which IS leader Abu Bakr al-Baghdadi asks what Muslims are doing to avenge
deaths in Iraq