The shootings occurred on the outskirts of Half Moon Bay, a city about 30 miles (48 kilometers) south of San Francisco.

Officers arrested 67-year-old Chunli Zhao in connection with the shooting, the sheriff’s office said.

Officials believe Zhao is a worker at one of the facilities and that the victims were workers as well. Some workers at one facility lived on the premises and children may have witnessed the shooting, Corpus said. The connection between the new facilities wasn’t clear.

Corpus said officials hadn’t determined a motive for the shooting, though county Board of Supervisors President Dave Pine described the suspect as a “disgruntled worker.”

The shooting was the nation’s sixth mass shooting this year — and followed the killing of 11 people late Saturday at a ballroom dance hall in Southern California.

The sheriff’s Office first received reports of a shooting just before 2:30 p.m. and found four people dead from gunshot wounds and a fifth injured person at the first scene. Shortly thereafter, officers found three more people dead from gunshot wounds at a second location nearby, Capt. Eamonn Allen said in a news release.

About two hours after first responding, a sheriff’s deputy found the suspect, Zhao, in his car at a sheriff’s station in Half Moon Bay. He was taken into custody and a weapon was found in his vehicle. The sheriff’s department believes he acted alone, Allen said.

“We’re still trying to understand exactly what happened and why, but it’s just incredibly, incredibly tragic,” said state Sen. Josh Becker, who represents the area and called it “a very close-knit” agricultural community.

Aerial television images showed police officers collecting evidence from a farm with dozens of greenhouses.

Half Moon Bay is a small coastal city with agricultural roots now home to about 12,000 people. The city and surrounding San Mateo County area is known for producing flowers as well as vegetables like brussel sprouts. The county allows cannabis farming in certain areas.

It’s a majority white community and about 5% of the population is Asian, according to Census data.

“We are sickened by today’s tragedy in Half Moon Bay,” Pine said. “We have not even had time to grieve for those lost in the terrible shooting in Monterey Park. Gun violence must stop.”

California Gov. Gavin Newsom tweeted that he was “at the hospital meeting with victims of a mass shooting when I get pulled away to be briefed about another shooting. This time in Half Moon Bay. Tragedy upon tragedy.”