A rookie New York Police Department officer who shot an unarmed man inside a housing project is going on trial.

Opening statements are set for Monday morning in the manslaughter case against Officer Peter Liang (lee-ANG'). The officer shot and killed 28-year-old Akai Gurley in 2014.

His lawyers have said the shooting was an accident, not a crime. They've also indicated Liang will take the witness stand.

Investigators say Liang was holding his flashlight and his gun when he fired a single round in a pitch black stairwell. The bullet bounced off a wall before striking Gurley, who was on the floor below him.

Prosecutors also say that the officer and his partner argued over whether to report the shooting to supervisors.