Samuel Cassidy prepared for years to unleash his rage.
He had weapons. He read up on terrorism and manifestos. He harbored bomb-making materials. He rigged his home to go up in an inferno as he set out to kill nine fellow employees at a light-rail hub in San Jose.
While he plotted intricately for a mass attack, appearing like a terrorist on a mission, his motive was much simpler: He just hated his co-workers.
That's the picture painted so far by law enforcement as detectives try to understand the pent-up animosity that Cassidy appears to have kindled for a decade against the people he worked alongside.