Man’s Decision to Help Boy Is a Fatal Choice : Crime: Victim had interrupted the theft of a moped from its 13-year-old owner. One of four robbers fires a lethal gunshot. Family had planned to move.

A man who had walked outside to make a telephone call was shot to death in Bell Friday night when he tried to stop four men from taking a moped from a 13-year-old boy, authorities said.

David Guillen, 32, was on his way from his King Avenue apartment to a nearby phone booth about 7:30 p.m. when he saw the men trying to rob a boy at Gage and King avenues, Los Angeles Sheriff’s Deputy Rafael Estrada said Saturday.

When Guillen told the robbers to leave, one of them pointed a gun at him and shot him in the chest, Estrada said. Guillen died a short time later at St. Francis Medical Center in Lynwood.

The deputy said no one has been arrested in the attack.

Guillen, who was to celebrate his 33rd birthday this month, had planned to move to Sacramento with his wife, Yvonne, who is five months pregnant, and his 21-month-old son, Alex. The couple had decided that Northern California was a safer place to raise a family, Yvonne Guillen said.

“I guess this was the big one,� she said Saturday in a telephone interview. “He’d seen a little kid getting pushed around and he was tired of that. Instead of walking around it or walking past it, he got into it. But that was the way David worked.�

Yvonne Guillen, 27, said her husband grew into the role of a good Samaritan from his work as a truck driver. “He was always helping other people,� she said. “Whenever there was somebody stranded or had a flat tire, there he was, helping out.�

The boy whom Guillen aided said Saturday that the experience was “like a nightmare for me.� He said he was walking home from a friend’s house with the moped, which the boy said he had built himself.

Four men were sitting in a car on King Avenue about to turn onto Gage when they got out of the car and knocked him down. “They told me, ‘Give me the mini-bike,’ and one of them said, ‘Let it go or else I’ll shoot you.’ � the boy said.

“When I didn’t let it go they pulled out the gun and then some guy came out from nowhere and told them to leave me alone.

“At first when they put the gun at me I thought it was fake,� the boy said. “When I heard the gunshot I thought, ‘Holy shoot, it was a real gun!’ �

As the assailants sped away in the car, Guillen staggered to a service station, Bob’s Service Center, where he told the owner of the shooting and then collapsed.

The station owner, Bob Cupp, said Guillen, whom he knew, looked queasy.

“He said, ‘I’ve been shot’ and that was it,� said Cupp, 57. “Then he just keeled over.�