The first batch of documents released show there were four incidents involving Sam Cassidy that were "elevated to management," some of which resulted in disciplinary action.
The first occurred on July 16, 2019, said VTA, when Cassidy was sent home without pay for two days for insubordination. The agency says he refused to "follow company policy in signing out a two-way radio that was necessary to perform his job."
In January 2020, Cassidy had a verbal altercation with a coworker. At the time, the coworker made a report to a supervisor, that another unnamed employee said about Cassidy: "He scares me. If someone was to go postal, it'd be him."
The individual refused to name the source of the comment. VTA said they couldn't find anything in Cassidy's disciplinary history to explain or support the concern.
VTA documents describe another incident in October 2020, when Cassidy refused to take a mandatory CPR certification, citing COVID-19 as a concern. "A number of reasonable accommodations were provided to the employee with no ultimate resolution," said VTA in a statement.
Finally, in November of last year, Cassidy misused radio equipment and then abruptly left for the day.
"After having trouble clocking in for a work shift, Cassidy inappropriately used a VTA two-way radio for personal communication, rather than for operational matters, which is against VTA policy. He left work without permission instead of resolving the problem," said the transit agency.
VTA said their initial search of documents have shown no complaints of racist or threatening remarks by Cassidy toward his coworkers. However, there are still "thousands of pages" that need to be reviewed.
In the days following the VTA railyard massacre, it started to become clear Cassidy had a long history of dissatisfaction with his employer.
He was once stopped by Customs and Border Protection while returning from the Philippines in 2016, sources told ABC News. He was stopped and searched because he was carrying books about terrorism and manifestos, according to three sources familiar with the investigation. CBP found he was also carrying a notebook that detailed hatred of his workplace, the Valley Transportation Authority.
"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 department said in a statement.
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