Man Fatally Stabbed in Pizza Restaurant : Crime: Victim crashes child’s birthday party and argues with his estranged girlfriend, the boy’s mother. She is arrested.

A man was fatally stabbed by his estranged girlfriend after he crashed a birthday party for her 3-year-old son Saturday night at a crowded family pizza restaurant in Granada Hills, police said.

Robert Bridges, 28, a millwright from Apple Valley, was stabbed once or twice in the chest in a quarrel with Cynthia Stafford, 23, of Pacoima, Los Angeles police Detective Ken Buscarino said.

Bridges died at about 8:30 a.m. Sunday at Holy Cross Medical Center in Mission Hills.

Stafford, who was described as unemployed, was being held without bail on suspicion of murder, police said.

The couple had lived together about six months before breaking up and Bridges apparently went to the restaurant to try to revive the relationship, Buscarino said.

The detective said Stafford went to the Chuck E. Cheese’s Pizza Time Theater with her son, about five other children and as many as 10 adult friends and relatives. Bridges showed up, uninvited, at about 7:30 p.m..

“He was not the boy’s father, but he had apparently befriended him when he was with the mother and somehow learned about the party,” the detective said.

The couple had a lengthy argument, Buscarino said. Stafford left the restaurant and walked to a nearby supermarket, where she bought a 10-inch steak knife and returned, the detective said.

The stabbing took place about 9 p.m. near a salad bar in a dining room, some distance away from the youngsters at the birthday party, who apparently did not witness it, Buscarino said.

However, the detective added, officers interviewed about 10 eyewitnesses.

“I’m sure a lot of people saw it and grabbed their kids and left as fast as they could,” Detective John Birrer said. “I’m surprised as many people hung around as they did by the time we got there.”

Buscarino said Bridges was aware that Stafford had a knife, but “he may have thought she was just threatening him. But he was wrong. She did him in.

“It went down quickly,” the detective said. “Bridges got stabbed and he didn’t fall down or scream. He was able to stand upright until his friends in the party drove him to the hospital.”

Stafford’s son was placed in the custody of his maternal grandmother, Buscarino said.

A woman, who identified herself as Stafford’s mother, said she was at work several weeks ago when her daughter phoned to report that Bridges was at the Pacoima home Stafford and her son share with her.

“He was just banging on the door. Pounding, pounding, pounding. I could hear it through the telephone,” the woman said. “I told my supervisor I had to leave because somebody’s trying to break into my house. When I got here, he was still pounding.

“Hell, he’s a damn nut, and I guess she is too,” the woman said of the victim and her daughter.

“It was her baby’s birthday party. This is what it started out as. And it turned into a tragedy.”

Times staff writer John Johnson contributed to this story.