SAN FRANCISCO (AP) — A farmworker charged with killing seven people last year in back-to-back shootings at two Northern California mushroom farms was indicted by a grand jury in an effort by prosecutors to move the case along, authorities said.

Chunli Zhao was in court Tuesday to be arraigned on seven counts of first-degree murder and one count of attempted first-degree murder, but his arraignment was continued until Feb. 29, San Mateo County District Attorney Steve Wagstaffe said in an email.

Zhao was charged last year in the Jan. 23, 2023, killings of seven people in Half Moon Bay. He pleaded not guilty last February. But the case has dragged on with a preliminary hearing not set until March, and that has now been vacated, Wagstaffe said.

The grand jury indictment supersedes the criminal complaint and bypasses the need for a preliminary hearing, skipping one step in the legal process and advancing the case, he said.

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“I know that extensive delays impose a very negative impact on victims’ families and we try to move cases along when the case seems to be dragging on. That is why we sought to seek the Grand Jury Indictment,” Wagstaffe said.

The next step is for Zhao to enter a plea on the grand jury indictment charges at the February hearing, he said.

Prosecutors say Zhao began the shooting rampage at California Terra Garden after his supervisor there demanded he pay a $100 repair bill for his forklift after he was involved in a crash with a co-worker’s bulldozer. They say he killed four co-workers and wounded another one before driving to Concord Farms, a mushroom farm he was fired from in 2015. There, he shot to death three former co-workers.

Zhao admitted to the shootings during a jailhouse media interview days after the killings and told KNTV-TV he was bullied and worked long hours on the farms.

The killings shed light on the substandard housing the farms provided to their workers. After the shooting, San Mateo County Supervisor Ray Mueller visited the housing at California Terra Garden, where some of its workers lived along with their families, and he described it as “deplorable” and “heartbreaking.”

Muller, who represents Half Moon Bay and other agricultural towns, posted photos on social media showing a shipping container and sheds used as homes.

Terra Garden’s owners agreed to build new permanent homes on a separate area of the farm for its employees and their families and provide them affordable housing during the year it would take to construct them. But a year after the shooting, permanent housing has not yet been built, the Mercury News reported.