The standoff had caused an hours-long shutdown of the 10 Freeway, backing up traffic for miles in both directions during the evening commute. The eastbound side was reopened around 7 p.m.
It ended when the suspect emerged from the front door carrying a long gun and was quickly shot by officers.
He was deceased at the scene.
During the standoff, it appeared the suspect set fires both within the home and on the porch of a neighboring house. He was also seen setting off fireworks in the yard.
At one point he was seen hiding under a truck with cigarette in his mouth and two guns in his hands.
Firefighting efforts were hampered by the dangerous situation. SWAT officers helped firefighters hold hoses as they remained at a safe distance from the suspect's known location.
The situation unfolded in the area of Saxon Avenue and Brighton Street near the Del Mar exit on the freeway.
Because the home overlooks the freeway, the Los Angeles County Sheriff's Department asked the CHP to shut down the 10 on both sides just before the evening commute got underway. Traffic was backing up for miles in both directions as rush hour began, and officers were trying to divert cars onto surface streets.
It all started around 12:30 p.m. with a family disturbance, police said. The suspect is believed to be homeless, but has family members at the home. They called police about a family dispute involving a man with a gun.
When officers showed up on scene, gunfire was exchanged, although no injuries were reported. The man then barricaded himself inside as negotiators contacted him by phone and tried to convince him to surrender. He continued to shoot out the windows toward officers.
Police say the same suspect was also involved in an incident at the home two days ago in which he fired a shot at a car or home.
Hours into the barricade, smoke began pouring from the home's windows and roof, and eventually flames engulfed the roof.
The suspect was seen fleeing from a back door and then walking onto a neighbor's property. He tried to break in through the front door and at one point was rummaging through the neighbor's car. A small fire was also set on the porch of that home.
At one point he was also lighting boxes of fireworks and throwing them on the ground in the backyard.
The SWAT team evacuated nearby residences during the standoff. Crisis negotiators attempted to talk to the suspect, police said.
"The individual seems somewhat paranoid, believed that people were there to hurt him, and while trying to reason with the individual, it seemed that he was not willing to reason with us," said San Gabriel Police Capt. Fabian Valcdez.
It all ended around 6:40 p.m. when the suspect entered another residence and was apparently trying to set it on fire as well. The SWAT team used its heavy equipment to shoot hot gas into the residence to force the suspect out.
When he emerged he had a long gun in his hands and was immediately shot by officers.
"When he exited the location, a confrontation occurred and he was put down by the SWAT containment personnel," said Jim Hellmold, chief of the sheriff's department Special Operations Division.
Authorities later said it's not clear whether the deputy's round struck the suspect or if the wounds were self-inflicted.
No other injuries were reported in the incident. The suspect's name was not released.
The nearby neighborhood at Strathmore Avenue and Marshall Street was closed to residents and traffic for several hours. By late Thursday night, police were letting only residents in as the investigation continued into the night.