A gunman opened fire at a Korean Christian retreat center in Southern California Tuesday night, killing one person and wounding three others, authorities said.

The gunman was believed to be among the injured at the Kkottongnae Retreat Camp. Investigators were unsure what prompted the attack, sheriff's spokesman Dennis Gutierrez said.

"We have some nuns that are very distraught," Gutierrez said.

Gutierrez said at least two of the victims were critically injured. A nursing supervisor at the Inland Valley Regional Medical Center near the retreat said she had no information on any of the victims.

Police and emergency crews converged on the rural area off Highway 79 after receiving reports about 7 p.m. that a gunman had shot his wife, said Mario Lopez, a spokesman with the California Highway Patrol. He said one person was dead when they arrived and the other three were hospitalized.

Law enforcement officers interviewed people at what appeared to be a triage center for injured victims, but Gutierrez said the language barrier was making it difficult to get all the facts. He said investigators believe all the victims are over age 40.

The retreat is one of four U.S. branches of the Kkottongnae Brothers and Sisters of Jesus, a Catholic organization dedicated to serving the poor and homeless. It was founded in the city of Cheongju, South Korea, by Father Oh Woong Jin in 1976.

A woman who answered the phone at the group's Lynwood branch on Tuesday night said she did not speak English well and declined to discuss the shooting.

Kkottongnae means "flower village," according to the organization's Web site.

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Kkottongnae Web site: http://www.flower-vill.com