REDWOOD CITY, Calif. >> The shooting that left four dead at a California mushroom farm on Monday was at least the second time an employee tried to kill a coworker on the property, records show.

Martin Medina, a manager at California Terra Garden, was charged with attempted murder after he threatened to kill another manager and then fired a shot into the man’s trailer. The bullet went through the trailer and into a neighboring one that was home to Yetao Bing, one of the workers killed on Monday, a prosecutor told The Associated Press. No one was injured.

Law enforcement interviewed Bing’s wife, Ping Yang, but it’s not clear from those interviews whether Bing was at home during the shooting, said Sean Gallagher, chief deputy district attorney for San Mateo County.

Medina remains in custody on $5 million bail and appeared in court Monday for a preliminary hearing, hours before authorities say Chunli Zhao shot and killed four coworkers and wounded a fifth at California Terra Garden. Prosecutors say Zhao then drove to a nearby farm where he used to work and killed three more people.

The Bay Area News Group first reported last summer’s shooting.

Zhao, 66, told KNTV-TV in a courthouse interview Thursday that he committed the fatal shootings. Zhao said he was bullied and worked long hours on the farms and that his complaints were ignored, the station reported.

Eric Hove, one of Zhao’s attorneys, did not immediately respond to a phone message seeking comment.

Zhao spoke in Mandarin with the television station reporter during a 15-minute interview at a county jail in Redwood City. Zhao said he has been in the U.S. for 11 years and has a green card. He said he has a 40-year-old daughter in China and lived with his wife in Half Moon Bay.

Zhao told the station he bought the gun used in the killings in 2021 and didn’t run into any obstacles when making the purchase. He was planning to turn himself in to authorities when he was spotted by deputies who arrested him Monday.

The San Mateo County District Attorney’s Office has declined to release information from an interview Zhao gave to investigators after he was arrested.

David Oates, California Terra Garden spokesman, confirmed Zhao lived on the farm along with his wife and said the farm has “no knowledge of any complaints by anyone on allegations of bullying.”

Huizhong Li said he hired Zhao in January 2016 at Mountain Mushroom Farm, which is now California Terrace Garden.

Li, a longtime mushroom farmer, said living conditions were not too comfortable but that working conditions were pretty good. He said, though, that Zhao would tattle on people he didn’t like, to Li.

“He likes to take advantage of small things. Let’s say he doesn’t like somebody, he likes to report things,” Li said in Mandarin.

Zhao spoke of returning to China to retire but Li did not know anything about when Zhao moved to the U.S. or how he wound up in California. Zhao’s wife lived on the farm with him but did not work there, Li said. Li stopped running the farm in 2017.

The charges against Zhao include additional allegations that could result in the death penalty or life in prison without parole, though Gov. Gavin Newsom has issued a moratorium on executions. Among those allegations are that Zhao used a gun, caused great bodily injury and killed multiple people.

The coroner’s office named six of the victims: Zhishen Liu, 73, of San Francisco; Marciano Martinez Jimenez, 50, of Moss Beach, California; Aixiang Zhang, 74, of San Francisco; Qizhong Cheng, 66, of Half Moon Bay; Jingzhi Lu, 64, of Half Moon Bay; and Bing, 43, whose hometown was unknown.

The charging documents identify Jose Romero Perez as the other person killed and Pedro Romero Perez as the eighth victim, who survived the shooting.

Few details about the victims are known, but officials have said some were migrant workers. Chinese workers make up a small percentage of the farmworker population in the coastal region.

The state’s labor department is looking into possible labor, workplace safety and health violations at the farms where the shootings happened, a spokeswoman for the Department of Industrial Relations said Thursday. Newsom’s office said some of the farmworkers told him they made $9 an hour and lived in shipping containers. The state minimum wage is $15.50.

“The conditions farmworkers shared with the Governor … are simply deplorable. Many workers have no choice but to tolerate the conditions provided to them by their employers,” Newsom spokesperson Daniel Villaseñor said in a statement.