FRESNO, California – A poultry processing plant employee opened fire on his co-workers on Tuesday, killing two men and injuring two other people before fatally wounding himself with a bullet to the head, authorities said.

Fresno police Lieutenant Don Gross said the shooter opened fire in a single room and that, with machinery operating, it was loud and some of those shot may not have known they were coming under fire. At least three of them were wearing ear protection to block out noise, he said.

The gunman, identified as Lawrence Jones, 42, had a criminal history and was found by officers on the sidewalk near the plant with a self-inflicted gunshot wound to the head, Police Chief Jerry Dyer told reporters. He was taken to a hospital in critical condition but was later pronounced dead.

Plant worker Salvador Diaz, 32, was shot in the head and pronounced dead at the scene, Gross said. Also killed was Manuel Verdin, 34, another worker at the plant who also was shot in the head, transported to a hospital and later died, he said.

Fresno County Coroner Dr. David Hadden said another person was saved when the shooter aimed the gun and pulled the trigger, only to discover he had run out of bullets in his four-shot revolver. The shooter later reloaded to kill himself, he said.

A 28-year-old male employee was hit in the neck and was hospitalized in critical condition, Gross said. A 32-year-old woman was shot in the buttocks, but is in stable condition, he said.

About 30 workers inside the plant are believed to have witnessed the shooting, and roughly another 30 were there but did not see what happened, Dyer said.

Dyer initially said the plant is called Apple Valley Farms, but Fresno city spokesman Michael Lukens later said the business recently changed its name to Valley Protein. The facility processes poultry, he said.

It appears Jones walked up to his victims and shot them from close range, Hadden said. The coroner called the shooter’s gun an “unusual weapon” with four barrels, instead of the usual one.

Fresno, a city with a population of about 500,000, is located 160 miles southeast of San Francisco and is surrounded by farmland in the San Joaquin Valley.

“This was a senseless, violent act that affects our entire community,” Mayor Ashley Swearengin said in a statement.

Dyer said police hope to determine a motive for the shooting.

TEST FOR DRUGS, ALCOHOL

Hadden said his office will perform a toxicology test on Jones and that he “very interested” in learning whether the shooter was using drugs or alcohol.

Jones reported for work before dawn and his coworkers noticed that he “did not appear to be himself,” Dyer said. Jones was at the plant for more than three hours before opening fire with a handgun, Dyer said.

“It’s difficult to say if there was a specific target that Jones was looking for,” he said.

A representative for Valley Protein could not be reached for comment.

Jones worked at the plant for the past 14 months and had a criminal history dating to the 1990s, Dyer said. His past crimes included auto theft and home invasion robbery, Gross said.

A woman who works at the plant, but declined to give her name, told reporters in Spanish that she saw the gunman move from table to table at the plant as he opened fire.

“He didn’t say anything,” she said. “He just went in silently with his gun.”

After the shooting, Janette Ramos stood outside the plant waiting for her daughter, an employee who eventually came outside and waved at her mom from beyond the police tape.

“Oh thank God,” Ramos said, as she walked to her daughter.

(Writing by Alex Dobuzinskis; Editing by Stacey Joyce and Cynthia Osterman)