A disgruntled employee shot and seriously wounded three co-workers at a menu printing plant Monday before killing himself as a SWAT team entered the building, authorities said.

The man, about 67, entered Kenyon Press shortly after 9 a.m., walked past a superior and opened fire on three co-workers with a semiautomatic handgun, said police Capt. Mary Risinger.

The business owner told police the man had indicated he was upset about a reduction in work affecting all employees, Risinger said.

"The employees recently had their hours cut back," Risinger said. "So he was upset about that, about not having enough work."

Names of the shooter and victims weren't released. The wounded were men in their 50s, said Valarie Carlomagno, secretary to the police chief.

It was not known how long the gunman had worked there or when the cutback was announced.

A dozen workers were in the business at the time of the attack. A female worker locked herself in a room and called 911 when the shooting started.

By the time police arrived some employees, including two of the wounded, had evacuated. Officers got the other employees and the remaining wounded man out of the building.

Ray 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."

One of the wounded had a torso injury and another had an arm injury, said Luna, whose own workplace was evacuated.

"It was pretty scary. At any point we were ready to hit the deck," he said.

Authorities initially reported the victims were in critical condition. They were later upgraded to serious.

The total number of shots fired wasn't known, Riesinger said.

The SWAT operation was conducted by a team from neighboring Long Beach.

Kenyon Press, which makes custom designed menus, has customer service personnel, copywriters, designers, illustrators, proofreaders, prepress, press and bindery/manufacturing workers.

Its clientele includes 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.