Long Beach, Ca – The 77-year-old man who fatally shot a fire captain, and wounded another firefighter and resident of his building, may not been trying to ambush first responders when he set the fire early Monday morning, as was originally believed.

Investigators initially thought that Thomas Kim, 77, was trying to lure firefighters to his apartment when he caused an explosion and fire in his senior-living, high-rise apartment building located in the 600-block of East 4th Street.

But on Wednesday, Long Beach police said Kim was having a dispute with his upstairs neighbor, and was likely trying to blow up the neighbor and himself early Monday morning, not lure firefighters to his apartment so they could be shot, CNN reported.

The incident began when firefighters were called to Covenant Manor, a senior and disabled-living facility located in the 600-block of East 4th Street, at about 3:50 a.m. on June 25 for a report of an explosion followed by a fire, KTLA reported.

Residents reported that they had heard an explosion and then afterward, smelled gas.

Firefighters arrived on the scene and found windows had been blown out of one unit in the building, and the sprinkler system had been activated, Long Beach Fire Chief Mike DuRee said during a press conference after the incident.

Chief DuRee said firefighters had knocked down the initial blaze and were searching the building when Kim opened fire from the end of the hallway near his apartment, killing Long Beach Fire Captain Dave Rosa and wounding another firefighter, 35-year-old Ernesto Torres, The Washington Post reported.

Kim’s bullets also struck another elderly resident of the retirement complex, who was taken to St. Mary’s Medical Center in critical condition. That victim’s name had not been released.

Long Beach Police Chief Robert Luna said police found two additional suspicious devices on Monday in Kim’s second-floor apartment where the explosion took place, and rendered both safe.

Police also removed gasoline from Kim’s apartment, and recovered a revolver, the chief said.

Neighbors said Kim had been in a dispute with the woman who lived above him and had called police about her several times, CNN reported.

Sue Windmiller-Smith told KCAL that she knew the shooter, and said she was in “total shock” after hearing what Kim had done.

“I do know that he was upset with the lady above him,” Windmiller-Smith said. “He was saying she was making noise in the night, and he would call the police and have the police go up there.”

Another neighbor was using the stairwell trying to evacuate the building with other residents during the incident when he encountered Kim, who was holding a gun.

Rick Convay said that after he spotted the armed man, they reversed direction and exited the building another way, and then told police what they had seen.

Kim was arrested at the scene, and has been charged with one count of murder, one count of attempted murder of a firefighter, two counts of attempted murder, one count of arson of an inhabited structure and one count of explosion with intent to murder, CNN reported. He could face the death penalty or life in state prison without the possibility of parole if convicted of those charges.

The community of Long Beach was in mourning for 45-year-old Captain Rosa, who is survived by a wife and two children.

Captain Rosa was a devout Little League volunteer, and KCAL reported that the players honored the fallen hero at an all-star game on Tuesday night.

“He was as good a guy as you’re ever gonna find,” Todd Strane, with the San Juan Capistrano Little League, said. “For such a good guy, you think about his family, you think about his wife, you think about his two boys, and they’re gonna go home today without a father. It’s sad.”

A memorial service for Captain Rosa has been scheduled for July 3 in the arena of the Long Beach Convention Center, according to a tweet posted by the Long Beach Fire Department.