SAN JOSE, CALIF. – On Jan. 23, seven individuals were shot and killed and one injured in Half Moon Bay, making it California’s second mass shooting of the year.

Officials on Tuesday said the tragedy appeared to be a case of workplace violence. According to CNN news, ¨The man suspected of killing four people at a California mushroom farm and three others at a nearby site Monday had legal possession of a semi-automatic weapon that was registered to him, a sheriff said.”

The 66 year old suspect, Chunli Zhao, worked with the victims at a mountain mushroom farm. Zhao acknowledged to NBC Bay Area’s Janelle Wang in a jailhouse interview that he killed the victims because he believed he had been the target of years of bullying. 

Zhao admitted to investigators that he had a disagreement with a supervisor before going on the fatal attack over paying for repairs to a forklift he was using that was damaged when, in his account, a coworker purposefully hit it with a bulldozer and that the damage was not his responsibility.

According to the allegation, Zhao then went to the coworker’s trailer and specifically targeted the victim’s wife. I killed your husband; you should join him too, he allegedly informed her. Then, according to NBC Bay Area, he went to another trailer, killed a coworker, murdered his brother, and then drove to Concord Farms on Highway 1 and killed three more people he had a grudge against.

Zhao was unknown to local law enforcement before the shooting, and as far as the sheriff’s office was concerned, there were no warning signs, according to San Mateo County Sheriff Christina Corpus.

The San Mateo District Attorney’s Office has charged Zhao with seven charges of murder and one count of attempted murder.

All of the murder charges come with enhancements for the use of a weapon, severe bodily harm, and multiple murder. A plea from the suspect is anticipated at the hearing on Feb. 16.