SAN JOSE (CBS SF) — As Samuel Cassidy was in the midst of his deadly rampage at the Valley Transit Authority railyard, he was recorded on a security camera calmly strolling between the two buildings where he killed nine co-workers in a hail of bullets.

Santa Clara County Sheriff Laurie Smith said the gunman had three different semi-automatic handguns and fired about “39 rounds” before killing himself as San Jose police officers and sheriff’s deputies bared down on him.

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The gunman also apparently targeted many or all of his victims.

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

Light rail service was still down early Friday as investigators from Santa Clara County, the FBI and ATF continued to methodically search every square inch of the yard after an explosives dog alerted on a scent.

Jeff Harp, former assistant special agent in charge of the San Francisco FBI office, told KPIX 5 the concern was for possible booby traps left behind.

“This guy worked for VTA for sometime, 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,” he said.

In the video, Cassidy is seen walking by himself across the railyard that is nearly empty of trains during the morning rush hour. Harp said the gunman likely knew law enforcement would quickly respond to the scene.

“He was certainly aware that VTA was in close proximity to the sheriff’s department,” Harp told KPIX 5. “He knew that. He’d worked there for years. He knew it was going to happen quick.”

Federal authorities revealed Thursday that he had been stopped by Customs and Border Protection officers in 2016 while returning home from the Philippines over writings about terrorism and workplace violence.

On Thursday night, hundreds gathered outside San Jose City Hall to mourn alongside the families of the slain VTA employees.

“My dad was a selfless man, as a veteran, I know my dad wouldn’t have run away from the danger,” said Timothy Romo’s son Tristan Romo.

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Mass Shooting Victims in San Jose

VTA San Jose Shooting Victims (click image to enlarge)

Among stories recounted by the victims’ relatives were some acts of heroism that have been reported by survivors of the massacre.

Co-workers have told the family of Taptejdeep Singh that he saved many of their lives.

“When he heard the shots, when he saw everybody’s life in danger, his first reaction was to tell other people,” said Singh’s younger brother Karmen Singh. “He was calling his coworkers, telling them to hide under benches, figuring out what to do, how he could help.”

Singh, a father of two and husband, was ultimately shot and killed.

Paul Megia, an assistant superintendent at the VTA, also died after he reportedly saved a co-worker’s life by telling her to hide in his office.

“Tomorrow he was supposed to go to Disneyland,” his father Leonard Megia said. “That day, yesterday, he wasn’t even supposed to go to work. He was supposed to work at home and I was going to have breakfast with him.”

Stories of bravery and selflessness in the face of danger were numerous. Some family members said the victims loved going to work every day and that the VTA was like family.

A memorial of flowers and signs grew in size outside city hall and candles burned into the night.

Alejandra Rojas attended the vigil and placed a picture of her friend and shooting victim Adrian Balleza at one of the memorials. She said Balleza had got married only two years ago and had a toddler.

“He’s a great person, always smiling,” Rojas said.

“Never leave home without giving your loved one a kiss goodbye because that was the last I got,” Romo’s wife Annette Romo said.

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“God took my best friend and husband too soon and I’m wishing I could give him one last hug and tell him how much ‘I love you, I love you always,'” said Paul Megia’s wife Nicole Megia.