(NewsNation) — Shootings at two agricultural businesses on Monday in Northern California that left seven people dead and one injured are likely “workplace violence” incidents, police said Tuesday.

Police arrested 66-year-old Chunli Zhao from Half Moon Bay in connection with the shootings. He was eventually located in his car, which was in the parking lot of a sheriff’s substation. San Mateo County Sheriff’s spokesperson Eamonn Allen said the alleged shooter did not actively surrender to police, but declined to say why Zhao went to the sheriff’s substation.

Law enforcement authorities said Zhao legally purchased the semi-automatic handgun used in the carnage.

The only known connection the victims had to Zhao is that they may have been co-workers, San Mateo County Sheriff Christina Corpus said during a news conference a day after the shooting.

“Our hearts are broken,” Corpus said. “We’re working with the community together to heal from this tragic incident.”

The San Mateo County Sheriff’s Office first received reports of a shooting just before 2:30 p.m. Monday.

Four people were found dead, and one injured, at Mountain Mushroom Farm, where Zhao reportedly worked.

Officers found three more people dead from gunshot wounds at a second location about 5 miles away, Allen said in a news release.

Of the seven casualties, five are men and two women. One male was also injured. The coroner’s office is still working on identifying victims and notifying their next of kin, Corpus said — a task, she added, that may be made more difficult by the fact some of the victims were members of the migrant community.

Half Moon Bay is a small Northern California community of fewer than 12,000 people about 30 miles south of San Francisco.

The Half Moon Bay shooting followed the killing of 11 people late Saturday during a Lunar New Year celebration in Monterey Park, an Asian American community at the eastern edge of Los Angeles. The gunman killed himself as police approached his van the next day.

“You’re supposed to spend time with your family and your friends,” community member Hong Lee said. “Not trying to plan a funeral or mourn for your loved ones. It’s very devastating,”

President Joe Biden and first lady Jill Biden extended their sympathies for the Half Bay Moon shooting victims and their loved ones in a statement Tuesday morning.

“For the second time in recent days, California communities are mourning the loss of loved ones in a senseless act of gun violence,” Biden said. “I have directed my administration to ensure local authorities and the broader Half Moon Bay community have the full support of the federal government in the wake of this heinous attack.”

California Gov. Gavin Newsom tweeted that he was at a hospital meeting victims of the “deadly mass shooting” in Monterey Park when he was informed of the shootings in Half Moon Bay. “Tragedy upon tragedy,” he said.

According to a database compiled by The Associated Press, USA Today and Northeastern University, the new year has brought six mass killings in the U.S. in fewer than three weeks, accounting for 39 deaths. Three have occurred in California since Jan. 16.

The Associated Press contributed to this report.