An employee of a Fresno, California, meat processing plant shot four co-workers Tuesday, two of them fatally, before turning the gun on himself, police said.

The alleged gunman, 42-year-old Lawrence Jones, later died of a self-inflicted gunshot wound to the head, according to authorities.

The shooting occurred at Apple Valley Farms, where Jones had worked for 14 months.

Jones “did not appear to be himself” when he came to work Tuesday morning, police Chief Jerry Dyer said, citing one of Jones’ co-workers. The shooting began about 3 1/2 hours later.

A 32-year-old man with a gunshot wound to the head was pronounced dead at the scene. Jones was found outside the plant, police said.

Initially, police said three victims had survived the attack, including a 32-year-old woman who was found outside, shot in the lower back. The other victims were a 34-year-old man who appeared to have been shot in the head and a 28-year-old man shot in the neck, according to police.

It was not immediately clear which of the victims died.

Authorities don’t know what may have provoked the attack. Jones had an extensive criminal history, according to authorities.

As many as 30 workers were inside the business at the time, police said.

Community Regional Medical Center in Fresno told CNN it received four patients from Apple Valley Farms.

The business identified by authorities as Apple Valley Farms apparently goes by the name Valley Proteins.

Calling a phone number listed on a website as being for Apple Valley Farms led CNN to a voicemail for Valley Proteins, which said there was an emergency and that the business was closed for the day. Police also mentioned that some of the reports they received about the shooting used the name Valley Proteins.

On its website, Valley Proteins says it develops animal and pet food ingredients.