Investigators were trying to determine Tuesday why a 68-year-old man opened fire at a menu printing plant, wounding three co-workers who had apparently helped him land a job there.

Jose Mendez, of Hawthorne, killed himself as SWAT teams closed in the Kenyon Press offices Monday morning, police said.

Capt. Mary Risinger said the business owner told authorities Mendez had been upset that his hours had been cut back amid a company slowdown. The victims had apparently helped him get the job assembling menus there about a year earlier.

"We're as confused as everybody else," Risinger said. "If he was mad about the hours, he should have been mad with her, not the co-workers."

Mendez's longtime girlfriend, Gilma Newhouse, said Mendez hadn't worked since Feb. 9. "It's his only job; that's why he was so worried," Newhouse said in a phone interview.

She said she had no idea what prompted the attack.

"He only said 'I'll be back' when he left this morning and I said, 'OK,'" she said. "He didn't say anything to me about his work."

The attack began just after 9 a.m., when there were more than a dozen workers at the company. Mendez entered the plant and said "shut up" to someone before he began shooting, according to police. A female worker locked herself in a room and called 911. The owner wasn't there at the time, police said.

Rey Luna, 34, saw the chaos from a construction business where he works across the street.

"A lot of the employees looked like they were scared," said Luna. "Some of them were running from the back of the building. The other ones were coming out from the front door. And the cops were pulling them out with guns drawn and frisking them down."

The three victims were being treated at area hospitals. Rafael Mendoza, 46, was shot in the back and in the left elbow, and Sergio Garcia, 49, was wounded in the chest and shoulder, according to Long Beach Memorial Medical Center. Both were in fair condition late Monday, he said.

The name and condition of the third victim were not released.

Kenyon Press, which makes custom designed menus, has customer service personnel, copywriters, designers, illustrators, proofreaders, prepress, press and bindery/manufacturing workers. Its clients include Las Vegas casinos and hotel chains, according to its Web site.

Signal Hill, a city of about 11,000, is 20 miles south of Los Angeles, surrounded by the port city of Long Beach.