A New York City police officer was acquitted on Monday of murder and manslaughter charges in the off-duty killing of an unarmed man who the officer said attacked him last year during a late-night traffic dispute in Brooklyn.

The fatal shooting was captured on surveillance video and the footage was the foundation of the government’s case, which was first brought by the state attorney general under a new order to prosecute certain police killings. But the grainy, silent footage could not answer crucial questions about the encounter, and, as in other police shootings caught on video, the officer’s account proved pivotal.

The officer, Wayne Isaacs, testified in State Supreme Court in Brooklyn last week that he opened fire after the man, Delrawn Small, threatened to kill him and punched him at a stoplight in the Cypress Hills section of Brooklyn.

The surveillance video, which emerged almost a week after the incident, had raised questions about the officer’s account of the confrontation, which occurred just after midnight on July 4, 2016. The jury of five men and seven women deliberated over three days before deciding the government had not proved its case against Officer Isaacs.