Following the tragic events reported on Jan. 24, local police have charged 66-year old Chunlin Zhao with seven counts of murder.

The suspect, who the authorities believe acted alone, used a registered semi-automatic gun to shoot four people at the Mountain Mushroom Farm. 

He then drove to a nearby farm, where he was a former employee and shot another three people, AP News reports.

"There was nothing that would have alerted us or alerted us to have any concern with him at this time, prior to this incident," San Mateo County Sheriff Christina Corpus told CNN.

Corpus said that this appears to be a case where someone "snaps," and "innocent people were killed..".

Zhao was detained on Monday and will appear in court for an arraignment on February 16, after the judge decided to postpone Wednesday's hearing following a request by the defense. 

Although co-workers described Zhao as “polite and friendly”, this isn’t the first violent incident the suspect was involved in.

The San Francisco Chronicle reported in 2013 that Zhao was accused of threatening to “split a coworker’s head open with a knife” and separately tried to suffocate the man with a pillow,

He will remain in custody without bail.