At a news conference Monday, Federal Way Police Chief Brian Wilson said the shooting spree began about 9:30 p.m. when a 28-year-old man shot and killed his girlfriend in the unit where the lived together at Pinewood Apartments.
The man then went out into the parking lot where he confronted two other men and shot them both to death. Neither victim knew the gunman or his girlfriend, and one was shot in the back while trying to run away, officials said.
Wilson said the gunman also used a shotgun to blast open the door and murder a 62-year-old man inside a neighboring apartment after the man who lived there yelled for someone to call 911.
Investigators believe the gunman may have been trying to kill witnesses, according to Wilson.
Police officers raced to the scene and could hear shots still being fired as they arrived at the apartment complex.
Wilson said they confronted the armed man in a stairwell and fired several shots at him, wounding him, but he ran off. Officers regrouped and found the injured man a short distance away on the ground in the parking lot near where two of the other bodies were located.
As the officers approached, the man reached for a handgun and refused the officers' orders to not grab the weapon, Wilson said. When he continued to reach for the gun, several officers opened fire, killing the man.
Wilson said no officers were hurt, but it was not clear if the man actually fired any shots at police.
The man had a history of domestic disputes in Seattle and Federal Way, but they did not result in criminal charges and he had a valid permit to carry a concealed weapon, according to Wilson.
Those previous domestic violence incidents did not involve the woman who was murdered on Sunday. Wilson said the gunman was listed in internal police records with a caution note due to his history violence and tendency to carry weapons.
A total of eight officers fired their weapons during the confrontation on Sunday. All have been placed on administrative leave, per standard policy, as the investigation continues.
The names of the suspected killer and the victims have not been released.