SAN JOSE (CBS SF) — An arson blaze at the home of VTA railway shooter Samuel Cassidy was triggered by a pot of ammunition left slow-cooking on his stove and a kitchen sprayed with accelerants, authorities said as they wrapped up the fire investigation Friday.

Search teams also found a massive cache of weapons, ammunition and over a dozen Molotov cocktails inside the burned structure.

Firefighters responded to the fire at the home on Angmar Court minutes after Cassidy began his deadly rampage at the transit facility at 6:34 a.m. Wednesday about 9 miles away.

Investigators were trying to not only determine the motive behind the shooting that left nine co-workers dead, but also if the fire was set on a time delay to divert first responders away from the VTA yard.

“The intent was to burn down the house,” Santa Clara Sheriff Laurie Smith said. “He knew what he was doing.”

If the fire had ignited the cache, the explosion would have rocked the neighborhood and caused widespread damage.

“The ammunition in that pot would have heated to a point where the powders inside would have detonated and ignited the accelerants that were placed in the kitchen, causing that residence to catch fire,” said Santa Clara County Sheriff Sgt. Joseph Piazza.

Shortly after 2 p.m. Friday, investigators had left the scene and neighbors who lived within a block of the house were finally allowed to return home for the first time since Wednesday afternoon.

Police had evacuated the entire cul de sac where Cassidy lived plus two houses on the back side. Neighbors were eager to get back home and grateful that there was no more loss of life.

“I never expected him to have all that stuff inside,” said neighbor Doug Suh.

On Thursday, a neighbor told KPIX 5 she was shocked and in disbelief.

“What the hell? That’s crazy. Just right across the street too, you know? You never know,” said area resident Nima Agago.

When asked what kind of person would do such things, Agago replied, “Nasty, you know? Glad to hear he’s not here, you know? I don’t feel that anyone should die, but if you’re out here killing like eight people and are going to blow up other people’s houses? It’s probably better for the community that you’re no longer here.”