(SAN JOSE, Calif.) — Unexploded but completed Molotov cocktails were found inside the charred home of San Jose, California, mass shooting suspect Samuel Cassidy, multiple sources told ABC News.

It’s unclear why Cassidy had the homemade explosives, the sources said. He may have intended for them to accelerate the fire at his house, which was reported minutes after the shooting. The devices didn’t explode.

San Jose Fire Department spokesperson Erica Ray said on Friday that the search of Cassidy’s home is complicated by “heavy” damage to the now “uninhabitable” residence. The fire seemed to burn quickly, she added.

San Jose police spokesman Steve Aponte said a “hoarder situation” further hampered the search.

Beyond the Molotov cocktails, a bomb squad at Cassidy’s house found a suspicious package on Friday, but it was determined the package was only wires and batteries, not another potential bomb, Aponte told ABC News.

Authorities do not yet have a motive for why Cassidy, a Santa Clara Valley Transportation Authority employee, allegedly gunned down nine men at the VTA light rail yard Wednesday morning.

The Santa Clara County Sheriff’s Office described him as “a highly disgruntled VTA employee for many years,” saying that “may have contributed to why he targeted” his colleagues.

VTA worker Kirk Bertolet told ABC News that Cassidy was a loner who was “never a part of the group.”

Thirty-nine shots were fired, authorities said.

Cassidy died at the transit hub, apparently from a self-inflicted gunshot wound. He was found on the third floor of the building.

Three semi-automatic handguns and 32 high-capacity magazines were found at the site of the shooting, officials said Thursday. The suspect was found dead with two semi-automatic handguns and 11 magazines with ammunition nearby, authorities said.

The guns are believed to be legally purchased and didn’t appear to be modified, Santa Clara County Sheriff Laurie Smith said Thursday.

There were magazines that could hold up to 12 bullets, which are illegal in California, authorities said. There was no indication those were modified for rapid shooting, Smith said.

FBI Special Agent In Charge Craig Fair told ABC News Thursday that investigators have obtained surveillance footage that captures the shooter walking into the building before the incident. FBI agents are working five crime scenes within the site and will be mapping them out digitally to recreate the shooting, he said.

Bertolet, an employee, was in a secure room at the transit hub when shots rang out. He said he felt helpless listening to the gunshots. When the shooter moved to another building, Bertolet said he ran to help his friends and coworkers but they were already dead.

Bertolet said he believes the shooter targeted his victims and spared others. He said the gunman looked at one of his coworkers, who was curled up on the floor, but didn’t shoot her.

“She was right among everybody else,” he said.

After the shooting, a police dog detected a suspicious device and a bomb squad began working to clear each room in the facility, authorities said. The explosive materials have since been traced to the suspect’s locker where Smith said authorities found precursor items to building explosives but no actual devices. Similar explosive materials were also found at his home, Smith said Thursday.

Given the timeline of 911 calls — an active shooter was reported at 6:34 a.m. and the fire reported at Cassidy’s home at 6:37 a.m. — Smith said authorities believe the suspect had a device set to ignite the fire. Smith said there’s no information to connect another suspect to the fire.

The point of origin for the fire has not been determined.

Beyond an arrest in the 1980s over a “minor” incident, authorities said there is no other known criminal history for the suspect.

Cassidy was questioned by Customs and Border Protection in 2016, three sources familiar with the probe told ABC News.

He was stopped by U.S. Customs and Border Protection agents while returning to the U.S. from the Philippines in August 2016. He allegedly was carrying books about terrorism and manifestos, which was the reason for the stop, sources said.

Cassidy was also allegedly carrying a notebook in which he wrote about his apparent hatred of his workplace, according to sources familiar with the matter. This development was first reported by The Wall Street Journal.

A Department of Homeland Security spokesperson declined to comment on the specifics of the case, citing the ongoing investigation, but said in a statement, “Under the leadership of Secretary [Alejandro] Mayorkas, in February, DHS commenced a department-wide review which included efforts to ensure law enforcement personnel have the tools and training to identify behavioral indicators associated with targeted violence and policy to improve information sharing with our partners.”

ABC News’ Kaylee Hartung, Alex Stone, Luke Barr and Jack Date contributed to this report.

Copyright © 2021, ABC Audio. All rights reserved.