LOS ANGELES -- A man with a semiautomatic rifle opened fire at a church festival Saturday, wounding his ex-wife and two bystanders before festival-goers grabbed him and held him for police, authorities and a church official said.

Gunfire rang out on a grassy field where the festival was being set up at the St. John Baptist de la Salle Roman Catholic parish shortly before 11 a.m., said police Capt. Steven Ruiz.

"We believe this is an isolated incident, a domestic-violence dispute," he said.

The man, whose identity was not immediately released, has a child who attends the church school but has had an ongoing dispute with the mother, Ruiz said.

He opened fire with a .22-caliber rifle a few minutes before the church's annual weekend festival was to begin. Father Robert Milbauer, the parish's pastor, said about 50 people, mainly church volunteers and their children, were busy setting up food and game booths and carnival-style rides when the gunfire erupted.

"I was walking toward the festival area to say an opening prayer and I saw them," Milbauer said of the shooting victims.

The man's 30-year-old ex-wife was one of the festival workers. She was hospitalized in stable condition, Ruiz said.

A 45-year-old man was shot in the chest and was in critical condition and another man, 47, was in stable condition with a leg wound, Ruiz said.

Their identities were not immediately released.

The man walked away after the shooting but was quickly grabbed by bystanders, one of whom was an off-duty police officer for the city of Burbank.

"They managed to overtake him and held him down," Ruiz said. "I'm told that he was in the process of possibly reloading."

The festival was shut down for the day, and Milbauer said grief counselors were meeting with witnesses, particularly the children.

"We'll have an evening Mass and we'll be praying for them at that time," he said of the wounded.

The parish plans to go ahead with the festival on Sunday, Milbauer said, in part to help parishioners put the tragedy behind them.

"We hope to be up and running and help people get beyond this," he said.

The church and school are located in the city's Granada Hills area in the San Fernando Valley, an ordinarily peaceful, multiethnic, middle-class residential neighborhood not far from the historic San Fernando Mission.

The annual festival features ethnic food booths, carnival games and rides. Proceeds go to the school's building fund.

"This is the only fundraiser that the parish has during the year," said Jerry Eckel, 62, a secretary in the religious education department.

There had been no major disturbances at the event in its 21 years, she said.

"It's a family event. There's no liquor involved," she said, adding the security is also provided.

The church, which has about 4,200 families in its congregation, has never been the scene of violence, she said.

"I'm just really shocked because I have been a member of the parish since I was 16 years old," she said. "I grew up there. It's home to us."