By Tim Molloy THE ASSOCIATED PRESS

GOLETA, Calif. – A former postal worker who had been put on medical leave for psychological problems shot five people to death at a huge mail-processing center and then killed herself in what was believed to be the nation’s deadliest workplace shooting ever carried out by a woman.

The attack Monday night was also the biggest bloodbath at a U.S. postal installation since a massacre 20 years ago helped give rise to the term “going postal.”

Investigators would not release the killer’s name or discuss a motive for the attack.

The rampage – the nation’s first deadly postal shooting in nearly eight years – sent employees running from the sprawling Southern California complex, and prompted authorities to warn nearby residents to stay indoors as they searched for the killer.

The 44-year-old woman had not worked at the plant for more than two years, but still managed to get inside the fenced and guarded Santa Barbara Processing and Distribution Center, apparently by driving her car close behind another vehicle through a gate, Santa Barbara County Sheriff Jim Anderson said.

She then opened fire with a 9 mm handgun, reloading at least once during the rampage, Anderson said.

Authorities found two people dead outside the plant, blocks from the University of California, Santa Barbara. Another body was just outside the door, and a wounded woman was just inside. Three more bodies – including that of the killer – were farther inside.

The wounded woman was hospitalized in critical condition. She had been shot in the head.

All of the killer’s victims were believed to be employees at the postal center.

Postal Inspector Randy DeGasperin said the woman was placed on medical leave in 2003 for psychological reasons. He said she had been removed from the building by sheriff’s deputies that year for acting strangely. She made no threats, but other workers were afraid she might hurt herself, authorities said.

DeGasperin said that it was unclear if she targeted certain people or fired at random, but “chances are she might have known her victims.”

The sheriff said the woman’s hair had been cut, and her appearance was different from when she worked at the plant. Her electronic pass card had been taken away when she stopped working at the facility, he said.

James Alan Fox, a criminologist at Northeastern University in Boston and an expert on homicides, said the death toll might be the highest ever for any workplace shooting carried out by a woman.

“Men, more than women, tend to view their self-worth by what they do” at work, Fox said.

Men also appear more prone to use violence in seeking revenge while “women tend to view murder as a last resort,” he said.

Postal employee Charles Kronick told KEYT-TV in Santa Barbara that he was inside the building when he heard shots.

“I heard something that sounded like a pop, and then I heard a couple seconds later, another pop, pop, pop,” Kronick said.

Kronick said his boss came running over and told him to get out of the building, and “we all hightailed it out real quick.”

Some 50 to 60 employees were seen running from the plant, and many fled to a fire station across the street.