Saipov drove a borrowed vehicle down a bike lane in Manhattan, New York, on October 31, 2017, as crowds of children and their parents prepared for Halloween celebrations. Saipov himself said after the crime that he had acted on behalf of the Islamic State (IS) jihadist militia. The IS referred to him as one of its "soldiers".

According to investigators, Saipov chose Halloween day for his crime in order to kill as many people as possible. In addition to the eight fatalities, at least twelve other people were injured, and the police were only able to stop Saipov with a shot in the stomach.

Prosecutors have sought the death penalty for Saipov despite Attorney General Merrick Garland declaring a federal moratorium on executions under the presidency of Joe Biden in July 2021. Garland had already allowed his agency to seek the death penalty in the Supreme Court in the case of Dzhokhar Tsarnaev, convicted of the 2013 Boston Marathon bombing.