Police spokeswoman Cathy Schrock said officers were called to the chaotic scene about 9:30 p.m. when someone reported gunshots at the Pinewood Apartments on Pacific Highway South.
"When officers arrived there were still shots being fired," Schrock said.
The officers saw two wounded men on the ground in the parking lot, and Schrock said one of the injured men reached for a gun as the officers approached. Several officers opened fire, killing the armed man. No officers were hurt.
The second wounded man died at the scene, and police found the bodies of three other people who had also been shot to death.
One man's body was found elsewhere in the parking lot, and the bodies of a man and woman were found inside separate apartment units.
Police believe the apartment where the man's body was found is where the shootings started, Schrock said.
A large contingent of police officers converged on the scene to help search the area, but by 11:30 p.m. officials said no one else was being sought in connection with the killings.
It was not clear what prompted the initial shootings, but Schrock described it as a firefight between all four men.
Schrock said investigators are trying to determine if the woman who was killed was hit by a stray bullet.
A total of eight officers fired their weapons, Schrock said. All have been placed on administrative leave, per standard policy, as the investigation continues.
By dawn, a King County medical examiner's office truck arrived at the scene to pick up bodies. Crime scene investigators continued working. One officer was seen carrying books and a gun to what appeared to be an evidence van.
No officers were hurt, and the names of the five people who were killed have not been released.
The Associated Press contributed to this report.