(CNN) The gunman who killed nine colleagues at a light rail yard in Northern California before taking his own life appeared to target his victims, a sheriff told CNN on Thursday.
During Wednesday morning's rampage at the Santa Clara Valley Transportation Authority (VTA) property in San Jose, the shooter -- identified as Sam Cassidy -- told a local union official there that "I'm not going to shoot you," Santa Clara County Sheriff Laurie Smith said.
The union official does not work for VTA, Smith said.
Cassidy, a VTA employee, fatally shot his coworkers inside two buildings around the time of a morning shift change before killing himself in front of responding law enforcement officers, authorities said. Authorities said Thursday they recovered three handguns, rather than two they initially said he carried.
The handguns were legally obtained and registered, the FBI San Francisco special agent in charge Craig Fair said Thursday.
In 2016, Cassidy was found with a memo book filled with notes of hatred toward VTA after US Customs and Border Protection officers searched his bags, a Department of Homeland Security official confirmed to CNN. Officers also found books about terrorism and fear and manifestos, the official said.
Cassidy was returning from a trip to the Philippines. The Wall Street Journal was the first to report information about CBP's search of Cassidy.
"Based on recent developments in the investigation we can say that the suspect has been a highly disgruntled VTA employee for many years, which may have contributed to why he targeted VTA employees," a news release from the Santa Clara County Sheriff's Office said Thursday.
The gunman fired 39 rounds, Smith told CNN. Authorities have said they are trying to determine the motive.
A witness told CNN affiliate KGO that he also believed the gunman bypassed certain people and appeared to select those he shot.
"He ... was targeting certain people. He walked by other people," VTA worker Kirk Bertolet told KGO on Wednesday night. "He let other people live as he gunned down other people."
The shooting is the latest example of America's gun violence scourge. It is the 232nd mass shooting -- which CNN also defines as a shooting in which at least four people were wounded or injured -- this year, according to a tally by the Gun Violence Archive. Seventeen such shootings have happened in the past week, a CNN analysis of the archive shows.
President Joe Biden reacted to the San Jose shooting by urging Congress to "take immediate action" on gun legislation.
"Enough," Biden said Wednesday. "Once again, I urge Congress to take immediate action and heed the call of the American people, including the vast majority of gun owners, to help end this epidemic of gun violence in America."
The San Jose killings are the latest against essential workers sustaining the US economy during the Covid-19 pandemic, following high-profile shootings including those in Indianapolis and Boulder, Colorado.
The property where the shooting happened is where vehicles of VTA -- a public transit operation that runs bus and light rail service -- are maintained and dispatched.
Those killed, who ranged in age from 29 to 63, were: Abdolvahab Alaghmandan, 63; Adrian Balleza, 29; Alex Ward Fritch, 49; Jose Dejesus Hernandez III, 35; Lars Kepler Lane, 63; Paul Delacruz Megia, 42; Timothy Michael Romo, 49; Michael Joseph Rudometkin, 40; and Taptejdeep Singh, 36, the Santa Clara County coroner's office said.
They will be honored Thursday night at an event at the San Jose City Hall plaza.
Emergency calls about the shooting began just after 6:30 a.m. PT, as employees from the midnight shift and the day shift overlapped, Santa Clara County Sheriff's Deputy Russell Davis said.
Minutes after authorities were called about the shooting, firefighters were called to a fire at the suspect's home in San Jose, Smith, the sheriff, told CNN on Thursday morning. It's not immediately clear how that fire started.
Fair, the FBI agent, told CNN that investigators recovered intact Molotov cocktails, made with paint thinners and alcohol, and multiple weapons at Cassidy's residence. No explosive materials were found in his locker.
The gunman shot people inside two buildings at the rail yard, Smith told CNN.
The shooter had three handguns and 11 magazines were found on his belt, Fair told CNN. Additional magazines, which hold more than 10 rounds and are illegal to possess in California, were also found at the crime scene.
"They were handguns of the type that would be legal in California," Smith said, adding she didn't know how or when the gunman obtained the weapons.
Deputies and other law enforcement officers arrived as the shooting continued, within two minutes of the calls, as the sheriff's office has a station nearby. They confronted the gunman on a building's third floor within six minutes, Smith told CNN.
The gunman "took his own life in front of the deputies," Smith told CNN. She said she believes the law enforcement officers' quick response saved many lives.
Investigators have found ammunition and "a lot more" at the gunman's house, said Smith, who didn't go into detail about the materials found there.
Cassidy resented his work, his ex-wife Cecilia Nelms told CNN affiliate the Bay Area News Group.
Nelms was married to Cassidy for about 10 years until the couple filed for divorce in 2005. She has not been in touch with her ex-husband for about 13 years, according to the outlet.
He often spoke angrily about his coworkers and bosses and at times directed his anger at her, Nelms told the outlet.
When the two were married, he "resented what he saw as unfair work assignments" and "would rant about his job when he got home," she said.
Cassidy had a strained relationship with an ex-girlfriend, court documents show, which revealed troubling allegations she made in a filing in 2009 as she responded to a restraining order he filed against her.
The woman says she dated Cassidy for about one year in what she said became an off-and-on-again relationship after about six months.
She described Cassidy as having mood swings that were "exacerbated when (Cassidy) consumed large quantities of alcohol," she said in the court document, and she alleged he had bipolar disorder.
She said he enjoyed playing mind games with her, according to the court document.
"Several times during the relationship he became intoxicated, enraged and forced himself on me sexually," said the former girlfriend, who CNN is not naming and is reaching out to for comment.
Surveillance video obtained by CNN shows a man leaving the home of the shooting suspect on Wednesday morning with a duffle bag.
A neighbor, who did not want to be identified, said the video was captured around 5:40 a.m. and showed Cassidy leaving the house in a truck. The neighbor described Cassidy as a "quiet" and "strange" man.
CNN has reached out to the sheriff's office to see if investigators have seen and are aware of this video.
The neighbor later noticed a fire broke out at Cassidy's home around 6:30 a.m.
The fire was reported at 6:37 a.m. -- a few minutes after calls about the shooting began, Smith, the sheriff, told CNN on Thursday.
No one was found inside the home, Mayor Sam Liccardo told CNN affiliate KGO.
Firefighters responded at a home in the 1100 block of Angmar Court in San Jose around the time that Smith provided, according to tweets from the San Jose Fire Department. That is about eight miles from the VTA facility.
It took firefighters about an hour to extinguish the two-alarm fire, which caused heavy damage and left the structure uninhabitable, the fire department said.