https://www.mercurynews.com/2021/06/10/he-scares-me-vta-documents-show-coworker-worried-future-mass-shooter-could-go-postal/

The gunman who killed nine of his Valley Transportation Authority coworkers was the subject of five investigations into his workplace conduct before he carried out the Bay Area’s deadliest mass shooting — including a chilling report that a colleague last year believed the man could “go postal,” the transit agency said.

VTA officials on Thursday described those investigations and released more than 200 pages of emails and other documents relating to 57-year-old Samuel Cassidy’s two-decade career with the authority. It was the first time VTA has acknowledged that co-workers raised concerns about Cassidy before he opened fire on colleagues at the authority’s light rail yard on May 26, then turned the gun on himself.