A California farm worker has been charged with seven counts of murder for a shooting spree that killed seven people, some of them his co-workers, in the state’s second deadly gun rampage in recent days.

The San Mateo County District Attorney charged Chunli Zhao, 66, the lone suspect in Monday’s massacre at two mushroom farms in the town of Half Moon Bay near San Francisco, with seven counts of murder and one count of attempted murder.

He is expected to appear before a judge at the San Mateo County Superior Court.

Zhao was charged with “special circumstances”, accused of “personally and intentionally” shooting to kill.

California law declares that defendants convicted of murder with “special circumstances” can be eligible for the death penalty, but Governor Gavin Newsom in 2019 declared a moratorium on executions.

Also on Wednesday, US Vice-President Kamala Harris, a California native, planned to travel to the Los Angeles suburb of Monterey Park, site of the first of the recent deadly rampages.

She was expected to meet some families of the 11 people who were fatally shot in a dance hall on Saturday night by a gunman who later took his own life.

Coming in quick succession, the two shooting sprees left California reeling from one of the bloodiest spates of mass gun violence in decades in a state with some of the strictest firearm laws in the United States.

Zhao was taken into custody on Monday evening outside a sheriff’s station, where police said he had driven shortly after the attack on farm workers.

Zhao had been employed by one of the growers, Mountain Mushroom Farm, and had resided at the property along with some other employees, according to California Terra Gardens, which owns the farm.

Authorities said early evidence indicated the bloodshed stemmed from a workplace grievance. The second crime scene, Concord Farms, is about 1.6 kilometres away.

The San Mateo County Coroner named six of the seven victims on Wednesday and listed their ages as between 43 and 73: Yetao Bing, Qizhong Cheng, Jingzhi Lu, Zhishen Liu, Aixiang Zhang, Jose Romero and Marciano Martinez Jimenez.

Two days before the Half Moon Bay killings, another gunman opened fire at the Star Ballroom Dance Studio, a club frequented mostly by older patrons of Asian descent in Monterey Park.

Eleven people died and nine were injured in Saturday night’s gunfire, which some survivors and bystanders said they initially mistook for fireworks as the predominantly Asian-American community was celebrating the Lunar New Year.

Authorities said the assailant, Huu Can Tran, 72, then drove to a second dance hall in neighbouring Alhambra. There, the club’s operator disarmed him before he could open fire.

The next morning, Tran fatally shot himself in his getaway vehicle as police closed in on him south of Los Angeles, leaving investigators with few clues as to his motive.