A man who was fired from a mental health center last year returned to the office Monday and opened fire with a handgun, killing one employee. Two others tackled the gunman as he reached for a shotgun, police said.

"They subdued him before he could do a lot worse," said Seth Katzman, an administrator at Conard House Inc. (search)

Gregory Gray (search), 54, of San Francisco, was arrested and charged with murder, police said. Katzman said he was fired from the center in September.

Police said they did not immediately know what motivated the attack or if the gunman was targeting the slain man.

Katzman identified the victim as Bruce Franks (search), a father of two who worked for Conard for about three years and also worked in homeless shelters.

"He was a good employee and a good guy who cared about his clients a lot," Katzman said. "I knew him well enough to respect him and to like him."

The attack occurred shortly before 9 a.m. at a Conard community service office in the downtown area.

Police said six employees were in the office when the gunman entered and opened fire. After he dropped a handgun and began reaching for a shotgun, police said a male case worker tackled him and yelled for help. That drew the attention of a client, who helped wrestle the man to the floor.

As the men struggled, a homeless man grabbed the shotgun, wrapped it in a coat and took it onto the street where he gave it to an arriving police officer, San Francisco police spokesman Neville Gittens said. The gunman was arrested soon after, he said.

The center provides mental health and social services to emotionally troubled adults and has helped administer some of the city's new "Care Not Cash" housing services for the homeless.