A gunman killed four people and two dogs and then shot himself to death at a Phoenix apartment complex on Saturday, police said.

Officers responded to an emergency call reporting shots fired around 9:15 a.m. local time, said Phoenix police spokesman Sergeant Tommy Thompson. They found a man whose apartment was damaged by gunfire but who was not wounded.

In trying to trace the source of the gunfire, the officers narrowed it to two possible units. When a witness reported seeing someone enter one of the residences, police sought to clear the neighboring unit and entered through the back patio, Thompson said.