The killings of seven people, gunned down in a small Northern California town, was an act of «workplace violence» that victimized members of the «migrant community,» authorities said Tuesday.

Suspect Chunli Zhao, a 66-year-old Half Moon Bay resident, worked at Mountain Mushroom Farm, one of two farm businesses where workers were killed Monday afternoon, authorities said.

«The only known connection between the victims and the suspect is that they may have been co-workers.» San Mateo County Sheriff Christina Corpus told reporters in nearby Redwood City. «All the evidence we have points to this being the case for workplace violence.»

Zhao was arrested in the parking lot of a Half Moon Bay sheriff’s substation shortly after the attacks.

“The semi-automatic handgun was legally purchased and possessed,” Corpus said.

FBI agents arrive at the scene of a shooting Monday in Half Moon Bay, California.Justin Sullivan/Getty Images

Sheriff’s investigators also said they are fighting to notify loved ones of the victims who were described as «members of the migrant community,» who were of Asian and Hispanic descent.

“As some of these victims were members of our migrant community, this presents a unique challenge when it comes to (survivor) notifications and identifications,” Corpus said.

While investigators did not immediately disclose what, if any, criminal history Zhao might have, it did not rise to any level of significant concern, authorities said.

«I will say there were no specific indicators that would have led us to believe that he was capable of doing something like this and we didn’t know him,» said Sheriff’s Capt. Eamonn Allen.

Zhao, who investigators had originally said was 67, is scheduled to make his first court appearance on Wednesday afternoon.

District Attorney Steve Wagstaffe called Monday’s attack the worst in San Mateo County history.

«We’ve never had one in this county with so many deaths … at the same time,» the prosecutor said. «So it’s a very eventful scene.»

«Jill and I are praying for those killed and injured in the latest tragic shooting in Half Moon Bay, California,» President Joe Biden said in a statement. White House statement issued Tuesday. «For the second time in recent days, California communities are mourning the loss of loved ones in a senseless act of gun violence.»

The Half Moon Bay murders occurred in the midst of a horrific 72-hour period of gun violence across California and the nation.

  • A man in Monterey Park, an Asian-majority suburb of Los Angeles, fatally shot 11 people at a Lunar New Year dance party Saturday night, authorities said.
  • A dozen people were injured early Sunday when gunfire erupted in a Baton Rouge, Louisiana, barthe police said.
  • Two students, ages 18 and 16, were shot Monday afternoon at a charter school in Des Moines, Iowa, which is designed for disadvantaged youth and has close ties to police, authorities said. An 18-year-old was arrested and faces two counts of murder.
  • Less than five hours after shooting began in Half Moon Bay, gunfire erupted 40 miles away in Oakland, where one person died and seven were injuredthe police said.
  • Three people were shot early Tuesday morning in Yakima, Washington, authorities said. A 21-year-old man is wanted in connection with the shooting at 3:30 a.m. PST at a Circle K convenience store.