Two days after the deadly mass shooting in San Jose, authorities were back at the Valley Transportation Authority rail yard and the shooter's home Friday, hoping to find more answers.
Investigators say they now know how a fire at the gunman's home, which happened at about the same time as the shooting massacre, may have started.
"A pot was placed on the stove in the kitchen of the residence. Investigators have determined that there was ammunition in that pot as well as accelerants around the pot. So, currently we believe that that pot overheated, causing that ammunition to discharge," Sgt. Joseph Piazza said.
At the rail yard, investigators discovered at least three semi-automatic handguns and 32 magazines. At the shooter's home, authorities found multiple cans of gasoline, suspected Molotov cocktails, 12 firearms and approximately 25,000 rounds of various types of ammunition.
The Santa Clara County Sheriff’s Office bomb squad and the San Jose Police Department's bomb team said they've completed a search of the rail yard and found no explosives.
Chilling surveillance video from a home across the street from the gunman's showed him get into his truck carrying a duffel bag. The homeowner who has that video says he had no idea it would play such a critical role in the investigation.
"You know, I didn’t think it was that important, that it was just fires," Doug Suh said. "I didn’t think it was that important. People started calling me. They wanted to see the security camera."
Investigators are still looking for a motive, but the sheriff's office said the shooter was "a highly disgruntled VTA employee for many years."
Neighbor John Zajac said the shooter kept to himself. But added a former neighbor had a run in with him after she took care of his dog.
"When she came back, the dog liked her better than him," Zajac said. "He got angry about it and he wouldn't talk to her anymore."
The shooter's father, James Cassidy spoke to the Mercury News on Friday.
He told the newspaper that his son was bipolar but the violence was unexpected. Cassidy also apologized to the victims' families.
"I don’t think anything I could say could ease their grief. I’m really, really, very sorry about that," he told the newspaper.