Dozens of firefighters stood at attention and saluted as the flag-draped coffin carrying Rosa's body was brought out of a hospital and loaded into a coroner's van.
Luna said a "person of interest" — who police believe is a resident at the facility — was detained at the scene and was being questioned by investigators. A weapon was recovered at the scene, he said.
"There is a big puzzle to put together," Luna said.
Investigators were looking into whether the shooter intentionally lured first responders to the scene to ambush them, Luna said.
"That's the environment we work in today, as law enforcement and firefighters. You go to these scenes and you never know what's on the other side of those doors. And these brave firefighters went through those doors and unfortunately they were met with gunfire," Luna said.
Pamela Barr, who lives in the building, said she was awakened by fire alarms and didn't panic because false alarms are not uncommon. She tried to go back to sleep but then learned what was happening by watching TV news. Firefighters later evacuated the building and put residents on buses.
"This is a lot to deal with," said Barr, 73, as she sat with her son in a car, waiting to be allowed back in the tower, where she lives on the ninth floor on the opposite end of the building from where the fire occurred.
Barr 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.
Gloria Ford, 58, who lives a few blocks away, was awakened by screaming sirens earlier and came to check out the scene.
"I'm very sorry about it. I'm sick about it," she said about the death of the firefighter. "It's just mad."
Police also called for bomb squad investigators after they discovered "a couple of devices they deemed to be suspicious."
The residential tower near downtown Long Beach has 100 apartments for low-income people age 62 and older as well as disabled adults over age 18, according to its website.
Long Beach is a major port city with a population of more than 400,000.
- AP