The suspect at a San Jose mass shooting that killed nine people at a California light-rail yard before committing suicide is believed to have had grudges against his coworkers, officials said on Thursday.

One official from United States President Joe Biden’s administration said the gunman expressed his dislike for the company he was working for after he was detained in 2016 during a trip to the Philippines.

Disgruntled Employee

Santa Clara County Sheriff Laurie Smith said the suspect, 57-year-old Samuel Cassidy arrived at his workplace’s, the Valley of Transportation Authority (VTA), light-rail facility in San Jose at around 6:00 a.m on Wednesday. She said he was carrying a duffel bag where he stored semi-automatic handguns and high-capacity magazines.

“It appears to us at this point that he said to one of the people there: ‘I’m not going to shoot you.’ And then he shot other people. So I imagine there was some kind of thought on who he wanted to shoot,” Smith said.

Kirk Bertolet has only started his shift when he heard gunfire nearby. On Thursday, he said Cassidy frequently worked with the victims. Bertolet said the shooter called them “a good bunch of blue-collar people.” However, he said Cassidy was more of a loner and outsider whenever he was at work.

“I know some of those guys, they’ll keep joking with you and they’ll keep hammering you about stuff. And if you’re thin-skinned and you can’t take it, I see that is the main cause of what’s going on,” Bertolet said.

Cassidy was classified as “a highly disgruntled VTA employee for many years,” sheriff’s officials said. They said it could have contributed to his mental condition and forced him to commit the heinous crime.

Bertolet said he believed the suspect was focused on killing specific people he worked with. He said Cassidy did not harm anyone he encountered while going from area to area looking for his targets.

“Sam made sure he killed all who he wanted. He made sure they were dead. I watched some of my coworkers breathe their last breaths, and they were all gone. Seven of them were just gone,” Bertolet said, ABC News reported.

When Cassidy was detained in 2016, officials found a memo book where he described his hatred for the Valley Transportation Authority. Details about his detention were not specific but it was noted that the suspect had books about “terrorism and fear and manifestos.”