DA: Workplace Grievance Fueled Half Moon Bay Massacre

The accused gunman in the Half Moon Bay massacre was motivated by perceived mistreatment at work, according to new details Thursday from the San Mateo County District Attorney's Office.

Chunli Zhao, 66, used a Ruger semi-automatic handgun at two farms on Monday to kill seven co-workers and wound the brother of one of the victims, prosecutors say.

Though officials were already describing the shootings as "workplace violence," it wasn't publicly specified until now that it involved the defendant's grievances against the fellow migrants he worked with.

The shootings at two separate mushroom farms marked the deadliest day in county history, officials said, and California's second mass shooting in as many days after the Monterey Park massacre that left 11 dead.

The seven murder counts against Zhao marked a record: DA Steve Wagstaffe said that's the most ever filed in a single case in San Mateo County. Combined with a count of attempted murder, a conviction could land Zhao in prison for the rest of his life—and possibly on death row.

Zhao, who was denied bail, is expected to enter a plea at his next court date, Feb. 16.