A retirement home resident has shot at firefighters who responded to a report of an explosion at the Southern California facility, killing a veteran fire captain and leaving a second firefighter and another resident wounded, officials say.
His motive was not immediately known.
Thomas Kim, 77, was arrested on suspicion of murder, attempted murder and arson after Monday morning's shooting in Long Beach, south of Los Angeles.
The shooting happened shortly after firefighters arrived at the 11-storey retirement facility around 4am and found some windows blown out, activated sprinklers, the smell of gas and a fire that they extinguished, authorities said.
Firefighters were searching the building when shots were fired and the two firefighters were hit, Long Beach Fire Chief Michael DuRee said.
Fire Captain Dave Rosa, who had worked for the department for 17 years, died at a hospital Monday morning, DuRee said. He is survived by a wife and two children - ages 16 and 25, the chief said.
The other firefighter, Ernesto Torres, was expected to make a full recovery.
An elderly resident at the retirement home was also shot and was in critical but stable condition, said Police Chief Robert Luna.
"Long Beach lost a hero today," Mayor Robert Garcia said.
Dozens of firefighters stood at attention and saluted as the flag-draped coffin carrying Rosa's body was brought out of a hospital Monday afternoon and loaded into a coroner's van.
Luna said a revolver was recovered after Kim was taken into custody Monday morning. Investigators were still working to determine Kim's motive and were examining whether he intentionally lured first responders to the scene to ambush them, Luna said.
Investigators also found two suspicious devices when they arrested Kim and called the bomb squad to render those safe.