The suspect behind the Jan. 23 mass shootings at Half Moon Bay told investigators he had been driven to the killings after a supervisor asked him to cover the cost of a work accident, officials said. Steve Wagstaffe, the San Mateo County district attorney, confirmed to the Bay Area News Group this week that Zhao Chunli recalled the farm equipment collision, where a forklift he was operating had been hit by a colleague driving a bulldozer. Zhao reported that his supervisor then demanded Zhao pay $100 to repair the equipment—despite his repeated insistence that it wasn’t his fault. Roughly half an hour before the shooting, Zhao confronted his supervisor about the bill, shooting both him and the colleague shortly after. Sources told NBC Bay Area that Zhao then returned to a trailer encampment and approached the co-worker’s wife, telling her, “I killed your husband; you should join him too.” Police said Zhao eventually killed seven people at two different mushroom farms in the area, and wounded an eighth man. In a courthouse interview with NBC Bay Area on Thursday, Zhao admitted that he was responsible for the shootings, saying he’d been bullied and ignored on the farm.