LONG BEACH, Calif. -- A 77-year-old man set a fire to lure firefighters to his Southern California retirement home so he could shoot them, authorities said. The attack killed one firefighter and wounded another.

Thomas Kim was arrested Monday on suspicion of murder, attempted murder and arson but investigators were still trying to determine a motive for the attack in the southern Los Angeles suburb, Police Chief Robert Luna said.

"There's still is a large puzzle we're trying to put together. There's still a lot of information we don't know," Luna said.

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Kim remained jailed on $2 million bail and it was unclear whether he had an attorney.

Firefighters were called to the 11-story Covenant Manor at around 4 a.m. Monday by reports of an explosion. They found some second-floor windows blown out, activated sprinklers, the smell of gas and a fire that they extinguished, authorities said.

Firefighters were searching the building when shots rang out and the two firefighters were hit, Fire Chief Michael DuRee said.

Fire Capt. Dave Rosa, a 17-year veteran, died at a hospital, the chief said. He is survived by a wife and two children ages 16 and 25.

"Long Beach lost a hero today," Mayor Robert Garcia said.

Capt. David Rosa in undated photo Long Beach FD

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. Community members waved American flags along the street outside the hospital as the procession of police and fire vehicles escorted the van to the coroner's office.

The other firefighter, Ernesto Torres, was released from the hospital and was expected to make a full recovery, officials said.

An elderly resident at the retirement home was also shot and was in serious but stable condition, reports CBS Los Angeles.

Family, friends and strangers attended a vigil outside the firehouse where Rose worked, the station says.

"Anytime we needed him, he was always here," one area resident said. "Christmas, Halloween. He was just full of joy."

However, the circumstances of that shooting were not immediately known.

The police chief said a revolver was found after Kim was arrested. Investigators also called in a bomb squad to render two suspicious devices safe.

Luna didn't explain the nature of the devices but said detectives have "a lot of questions" about them and what Kim intended to do with them.

Eighty senior citizens were evacuated from the retirement home until it could be declared safe.

"This is a lot to deal with," said Pamela Barr, 73, as she sat with her son in a car, waiting to be allowed back in the tower.

Barr, who lives on the ninth floor, said she hadn't heard of any troubles involving residents of the facility, where she has lived for seven years. She described it as clean, well-run and secure.

The residential tower near downtown Long Beach has 100 apartments for low-income people age 62 and older as well as disabled adults, according to its website.

Long Beach is a major port city with a population of more than 400,000.