A Southern California firefighter was killed and a second was wounded after an early Monday shooting at a California senior-living apartment complex, officials said.

Firefighters responding to a report of an explosion at Covenant Manor in Long Beach were met with gunfire, fire department Jake Heflin said.

Officials identified the victim as Long Beach Fire Capt. Dave Rosa, a 17-year veteran of the fire department. The second injured firefighter wasn’t immediately identified, but was released from the hospital late Monday morning.

“This is a tough day,” Long Beach Fire Chief Mike DuRee said at a press conference.

A third person was wounded in the shooting, but their condition was unclear.

The suspected shooter was in custody, police said. The person’s identity wasn’t immediately released.

“It's a very stressful situation,” Heflin said. “This is a very serious day for us.”

Long Beach police said they were investigating whether an explosion was used to get first responders to the building.

“There was a lot of commotion,” witness Dan Rafferty told CBS Los Angeles. Rafferty captured SWAT officers evacuating residents out of the building.

Covenant Manor is an apartment complex for low-income senior citizens.