Jurors were read several e-mail messages written by Alexander months before the killings that showed he had considered violence. "I'm going to smoke 'em," he wrote to a friend a few months before the slayings. "I'm going to shoot them execution style. Boom. Boom."
"He told several people he was going to do it and waited until he had built up enough courage to act," said Jack Laettner, an assistant U.S. attorney who is prosecuting Alexander along with Paul Hora, a deputy Alameda County District Attorney.
The most damaging trial evidence was the surveillance video taken inside the factory.
After the first gunfire, the video showed Alexander leaving the room for several minutes while he chased the fourth inspector, Earl Willis, who waited outside. The video shows Alexander returning and, upon seeing the three inspectors were still alive, firing at them several more times at point-blank range.