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Ringo H.W. Chiu, Associated Press
Police officers in the office building that houses offices of Southern California Edison after a man armed with a rifle shot two people, then shot himself in Irwindale, Calif., Friay, Dec. 16, 2011.

IRWINDALE, Calif. — Three people were killed and two more injured Friday in a California office complex shooting, police said.

The suspected gunman was among the dead and is believed to have self-inflicted wounds, Baldwin Park police Capt. Michael Taylor said.

"As far as we know there was one shooting suspect, period," Taylor said.

The shooting occurred around 1:30 p.m. Friday at Southern California Edison offices inside a larger office complex in Irwindale.

Edison International chairman and CEO Ted Craver confirmed that the victims and the suspected gunman were Southern California Edison employees, four full-timers and one contract worker.

Craver said "this is one of the most horrible days in our company's history."

One of the shooting victims was a woman and the other four were men.

Craver did not specify which were living or dead, and was careful not to provide identifying details for the victims, saying the company is still working to contact next of kin.

There was no immediate word on what prompted the gunfire.

Multiple media reports said at least two victims targeted by the gun-toting employee were believed to be company managers. Police said they could not confirm those reports.

One of the dead was discovered inside the building during a sweep, and police were continuing their search for more victims, said Taylor.

Another victim died en route to a hospital. The two wounded have unspecified injuries and their conditions are not known.

Taylor said police have not accounted for everyone in the building yet and were doing a sweep.

No gunfire was exchanged after officers arrived.

The building was quickly locked down and dozens of people were seen streaming out with their hands raised.

Gil Alexander, a spokesman for Southern California Edison, said the company has about 200 employees at the facility.

Alexander says the complex is a secured facility and employees need a security card to swipe at the doors before they can be admitted into the building.

Alexander called the incident "an enormous tragedy."

The utility's office is in a complex of buildings that also includes a business called California Lighting Sales.

Cindy Gutierrez, the controller for that company, said employees there didn't hear any shots fired and didn't realize anything was amiss until building management announced over the intercom that everyone should stay indoors.

Two nearby schools were locked for about two hours after the shooting and no one on the campuses was hurt prior to release.

Irwindale is a small industrial city of about 1,400 residents in the San Gabriel Valley, 22 miles east of downtown Los Angeles.

It is home to the popular Irwindale Speedway auto racetrack. It is also home to the annual Southern California Renaissance Pleasure Faire as well as sprawling rock and gravel quarries.

Southern California Edison is one of its largest companies, employing 2,100 people.