(05-15) 18:00 PDT SAN FRANCISCO --

A brawl that broke out during a birthday party in a public housing project in San Francisco's Bernal Heights neighborhood led to the fatal shootings of two men and the wounding of a third, witnesses said Sunday.

The shootings happened about 7:20 p.m. Saturday on the 100 block of Appleton Avenue at the Holly Courts housing project. Police revealed few details, but neighbors said the incident had grown out of a fight.

A man was being beaten up by four men when a friend of the victim fired a gun into the air, presumably to scare the assailants, said a neighbor who declined to give her name because she feared for her safety.

Friends of the assailants then converged on the scene and began firing back, she said.

"There's two people dead over some drunkenness," she said. "It got crazy too fast."

When police arrived, they found two men shot to death and a third with a wound that was not considered life-threatening. They said they had detained several people at the scene, but did not elaborate.

Authorities did not disclose the names of the victims, but family members said one of the dead men was Rathanuk Chea, 26. His brother Poenlou Chea, 30, was shot in the arm and was expected to be released from the hospital Monday, said Veasna "Dang" Chea, 32, their older brother.

It's not clear whether the brothers were involved in the fight, which broke out during the 31st birthday party for Ruben Collins. On Sunday, Collins sat on the patio inside Holly Courts where at least one of the victims was shot, mourning the death of a reveler he knew only as "Jerry."

Collins said he would not talk about the incident, but only about his friend.

"He was a young man at the beginning of his life," said Collins, 31, of Tracy, who was arranging liquor bottles on a bench as a memorial shrine. "It shouldn't have happened."

Members of the Chea family said they were struggling to find out more information.

"I'm in a state of shock," said Michael Tarbox, 55, who made a point of saying his nephews were never involved in gangs. "I used to babysit them. I was there when they were born. I had them all over to my house last week."

Rathanuk Chea was the youngest of four brothers, part of the family that founded Battambang Market, a Cambodian grocery in the Tenderloin. Their mother had been living in Cambodia for the past decade, but came to the United States just two weeks ago to care for an aging father, Chea said.

Rathanuk Chea, who worked in a restaurant supply store, had just moved to the Sunset District with his girlfriend and 7-year-old daughter, Veasna Chea said.

"He's an awesome, diligent father who worked hard to move his family out of the Tenderloin," Chea said. "He's a great person who was always willing to help his friends and family."

Chronicle staff writer Henry K. Lee contributed to this report.