SAN JOSE (CBS SF/AP) — A transit union president and officials with the Valley Transportation Authority have denied reports circulating that Samuel Cassidy, the VTA employee who killed nine people during a deadly rampage at a San Jose rail yard, was facing a disciplinary meeting the morning of the shooting.

A source had confirmed to KPIX 5 News Thursday night that such a meeting was to take place, but John Courtney, President of Amalgamated Transit Union Local 265, issued a statement saying that wasn’t the case.

UPDATE: Huge Arsenal of Weapons, Molotov Cocktails Cleared From VTA Shooter’s Home

“I wish to make it crystal clear that the ATU Local 265 officials who were at the site of this unfathomable tragedy were not — repeat not –there to attend any disciplinary or SkellyRights hearings or to respond to any jobsite or racial-oriented complaints,” Courtney said in his statement. “I was at the yard simply to check on working conditions and the continual safety of the dedicated men and women who work there.”

When asked Friday if a Cassidy disciplinary was scheduled for Wednesday, VTA officials simply said “No.”

Earlier Thursday, federal authorities confirmed that Cassidy had been detained by U.S. Customs agents five years ago because he had writings about terrorism and hating his workplace.

A federal official confirms to CBS News that Cassidy had been detained by U.S. Customs and Border Protection after returning to the States from the Philippines in 2016 due to the writings found in his possession. The Wall Street Journal first reported this.

According to the New York Times, in addition to a notebook that Cassidy had written in detailing how much he hated the VTA, officials found books on the subjects of terrorism and manifestoes.

Cassidy reportedly told agents he had no problems with people at work. The information regarding the 2016 incident is contained in a DHS memo concerning the encounter.

Cassidy fatally shot nine coworkers at a Santa Clara Valley Transportation Authority (VTA) rail yard before killing himself as law enforcement rushed the shooting scene.

Thursday afternoon, the Santa Clara County Sheriff’s Office issued an update on their investigation into the deadly incident that made note of Cassidy’s feelings towards his workplace.

“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,” the sheriff’s update read.

KPIX obtained a brief clip of surveillance video from the VTA light rail yard that showed Cassidy casually walking between the two buildings where he gunned down nine of his coworkers Wednesday morning.

“Right now, we think he fired about 39 rounds,” said Santa Clara County Sheriff Laurie Smith.

Smith told KPIX 5 that Cassidy picked out his victims–who would live and who would die.

“To one person he said, ‘I’m not going to shoot you.’ And then he started shooting others,” Smith explained.

The gunman had three semiautomatic handguns and 32 loaded high-capacity 12 round magazines, according to Smith. She had earlier incorrectly stated during a Thursday morning press conference that he only had two handguns and 11 high-capacity magazines.

A locker at the rail yard believed to be the gunman’s contained “materials for bombs, detonator cords, the precursors to an explosive,” Smith said.

“When our deputies went through the door, initially he was still firing rounds. When our deputy saw him, he took his life,” Smith told reporters.

Smith said the handguns he had appear to be legal but his high-capacity magazines are prohibited in California.

Additionally, Smith said the shooter appeared to to have a timer or device to set his home on fire 13 miles away from the VTA scene.

Jeff Harp, former assistant special agent in charge of the San Francisco FBI office says a concern is booby traps.

“This guy worked for VTA for some time so he knows all the nooks and crannies where police may look but not suspect and that’s where they’ve gotta be real careful,” Harp said.

Harp says everything that happened Wednesday — from the shooting to the fire at Cassidy’s south San Jose home — happened with this fact in mind: “He was certainly aware that VTA was in close proximity to the sheriff’s department. He knew that. He’d worked there for years. He knew it was going to happen quick.”

Cassidy’s ex-wife Cecilia Nelms told KPIX that while Cassidy had talked about harming co-workers, she never imagined anything like this.

UPDATE: VTA Officials Memorialize Employees Killed In Massacre

She said Cassidy also had anger issues but never physically hurt her. “I’m in shock, I’m very confused,” she said.

Nelms recalled how uncomfortable he was around other people. “Not a very friendly person, kept things to himself,” said Nelms.

Nelms said talk of killing his co-workers happened about a decade ago. “I never believed him, and it never happened. Until now,” a tearful Nelms told The Associated Press on Wednesday.

Samuel Cassidy (Santa Clara County Sheriff’s Office)

The number of people fatally shot by the gunman rose from eight after the Santa Clara County’s medical examiner-coroner late Wednesday confirmed the death of Alex Ward Fritch, 49. He had been wounded and hospitalized in critical condition after the attack.

READ MORE: Who Is Samuel Cassidy, Gunman In San Jose Mass Shooting At VTA Rail Yard?

It was the 15th mass killing in the nation this year, all of them shootings that have claimed at least four lives each for a total of 87 deaths, according to a database compiled by The Associated Press, USA Today and Northeastern University.

Gov. Gavin Newsom visited the site and then spoke emotionally about the country’s latest mass killing.

“There’s a numbness some of us are feeling about this. There’s a sameness to this,” he said. “It begs the damn question of what the hell is going on in the United States of America?”

It also was Santa Clara County’s second mass shooting in less than two years. A gunman killed three people and then himself at a popular garlic festival in Gilroy in July 2019.

Len Ramirez and Andria Borba contributed to this story

© Copyright 2021 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.