The northern California transit worker who shot dead nine of his co-workers this week was also under investigation for racist comments, according to local media.
Authorities say Samuel Cassidy, 57, opened fire on Wednesday at his workplace, a light rail station in San Jose.
Cassidy committed suicide minutes later as police arriving at the scene closed in, according to the county sheriff.
The sheriff said Friday that Cassidy had accumulated a dozen guns, Molotov cocktails and some 22,000 rounds of ammunition in his home – before setting them on fire.
She added that Cassidy was known to be a “very disgruntled” employee for many years, which may have motivated the attack.
But any attempt to pin down a specific motive can be complicated by the fire at Cassidy’s home, which destroyed much of the available evidence.
Local NBC affiliate KNTV, citing unidentified law enforcement sources, reported that Cassidy was recently accused of making racist remarks at work and faced a disciplinary hearing on the day. of the shooting.
But the outlet later backtracked on its report, after the county’s Valley Transportation Authority issued a statement denying the reports of any scheduled meeting.
The transport agency said it was examining Cassidy’s alleged history of “fearful or worried” remarks.
Cassidy’s ex-wife Cecilia Nelms also told local media that he complained about her colleagues and bosses and sometimes criticized her.
The Wall Street Journal, citing a Department of Homeland Security memo, reported that U.S. customs and border officials arrested Cassidy in 2016.
They found in his possession “books on terrorism” and a notebook full of notes expressing hatred of his workplace.
Wednesday’s killings are just the latest in a string of mass shootings across the United States over the past three months.