A U.S. federal judge sentenced a former Blackwater guard on Monday to 30 months in prison and two years probation for his part in the May 2009 shooting death of an unarmed Afghan civilian.

Prosecutors say Justin Cannon fired at the rear of a retreating vehicle following a nighttime automobile accident in his convoy. One passenger in the automobile was killed, along with a passerby who was walking his dog.

Cannon and a second Blackwater contractor – Christopher Drotleff – were convicted of involuntary manslaughter in the death of the man in the vehicle. Both were acquitted of charges of killing the passerby.

Both men said the shooting was in self-defense.

Drotleff was sentenced to three years in prison earlier this month for his part in the shooting.