NEW YORK — A police officer has been charged in the killing of an unarmed motorist during a road rage incident earlier this year while the officer was off duty, the officer’s lawyer said Monday.

Officer Wayne Isaacs was expected to surrender and appear in court in Brooklyn on Tuesday to face charges of murder and manslaughter, defense attorney Stephen Worth said without commenting further.

The office of Democratic state Attorney General Eric Schneiderman, which investigated the case, declined to discuss the charges.

It marks the first time the attorney general has prosecuted a police shooting of an unarmed victim since Democratic Gov. Andrew Cuomo gave the office that role in August 2015 in response to a spate of civilian killings by police caught on videotape.

The shooting of Delrawn Small occurred in the middle of the night on July 4 in Brooklyn while Isaacs was on the road in civilian clothes but still carrying a handgun following a tour that ended at midnight. A passenger in Small’s car told police Small grew angry because he thought Isaacs had cut him off and got out his car at a stoplight to confront the officer.

Based on preliminary evidence including Isaacs’ statements, police initially said they believed the officer opened fire after Small reached through an open driver’s side window and punched the officer while he sat behind the wheel of his car.

But a short black-and-white video, which surfaced on the internet, appears to show Small getting struck by gunfire the moment he walks up to the car window, with no clear indication that he first assaulted the officer.

Small, 37, can be seen recoiling and stumbling around before collapsing. The officer briefly exits his car and looks in the fallen man’s direction but then returns to the car.

Isaacs, also 37, was put on desk duty while the attorney general investigated.

Small’s estate has filed a $25 million wrongful-death claim against the city, said Sanford Rubenstein, a family attorney. The family welcomes the criminal charges and “is determined to fight for justice,” he said.