A man has killed his live-in girlfriend in Washington state before fatally shooting three men, including one who had phoned 911 to report hearing gunfire, police say.
Arriving officers found a chaotic scene at an apartment complex in Federal Way, about 20 miles (32km) south of Seattle.
Authorities say officers twice shot at the suspect in a stairway and in a parking lot. The 28-year-old man also died at the scene.
Federal Way Police Chief Brian Wilson said the suspect confronted officers with a shotgun. Police fired upon him, but he fled to a nearby parking lot.
There, Mr Wilson said police found him on the ground. When they approached him again he reached for a handgun, prompting officers to again open fire.
Chief Wilson said: "This is one of the most dangerous ... calls for law enforcement to respond to."
Neither the suspect nor the victims have been identified. Chief Wilson said the victims were the suspect's 25-year-old girlfriend, and three men, ages 24, 46 and 62.
Police were still piecing together information, but believe the suspect shot his girlfriend in the apartment. He then confronted two men, the 24-year-old and 46-year-old, argued with them and fatally shot them both, authorities said.
Chief Wilson said the 62-year-old man had heard the commotion from another apartment in the building, went outside to investigate then retreated inside his residence to call 911.
The suspect broke down that man's door with a shotgun and killed him, Chief Wilson said.
"When officers arrived there were still shots being fired," said Federal Way police spokeswoman Cathy Schrock.
After police flooded the area and carried out searches, authorities said they were confident there were no more casualties from the shooting.
By dawn, a King County medical examiner's office truck arrived at the scene to pick up bodies. Crime scene investigators continued working.
A total of eight officers fired their weapons, Ms Schrock said. All have been placed on administrative leave, per standard policy, as the investigation continues.
Chief Wilson said the suspect, who had a valid concealed weapons permit, had no criminal history.