Man Held in Freeway Stabbing : Crime: Police wound him after he reportedly attacked his mother with a screwdriver while driving. The car went over embankment in Glendale.

Los Angeles police shot an El Cajon man who had repeatedly stabbed his elderly mother with a screwdriver as their car swerved through traffic on the Golden State Freeway and went over an embankment in Glendale, authorities said Tuesday.

Barnabas Sanborn, 27, was arrested on suspicion of attempted murder after he stabbed his 72-year-old mother “15 to 20 times” during the Monday incident, continuing to attack her even after the crash, Los Angeles Police Detective William Thurston said.

“He just flipped out and started stabbing her as they were driving down the road,” California Highway Patrol Officer Huston Currie said.

Sanborn, shot in the arm when he ignored police orders to stop the attack, was in stable condition Tuesday in the jail ward at Los Angeles County-USC Medical Center. The bullet passed through his arm and lodged in his chest. His mother, Edith, was in critical condition at Holy Cross Medical Center in Mission Hills, Thurston said.

According to Los Angeles and Glendale police and CHP reports, Sanborn and his mother were arguing as he drove north on the freeway near Western Avenue about 8:15 p.m. when he apparently began stabbing her in the chest with a screwdriver. Edith Sanborn grabbed the steering wheel and the car swerved across a lane of traffic, grazing the rear bumper of another car before it went over the embankment, Currie said.

Two Los Angeles police officers driving past a few seconds later noticed a cloud of dust or smoke coming from the side of the road and pulled over. One car was parked at the side of the freeway and Sanborn’s car was about 20 feet down the embankment.

Officer Lance Nielsen, 24, walked down the embankment to the car. As he approached, a man who had leaned into the passenger’s side window to offer help jumped back and shouted: “He’s stabbing her.”

Nielsen, who has been a police officer for a year, looked through the rear window of the car and saw Sanborn stabbing his mother in the front seat, Thurston said. Nielsen ordered him to stop, but Sanborn ignored him, and the officer fired a single shot from his 9-millimeter handgun, Thurston said.

Sanborn stumbled out of the car and began to run, Thurston said. Neilsen and another officer chased him to Sonora Avenue and Flower Street about two blocks away, where he was arrested.

Relatives and neighbors in El Cajon said Sanborn lived with his mother, who was retired, in a small two-bedroom house. Sanborn worked odd jobs as an auto mechanic and helped his mother around the house, neighbors said.

The two argued sometimes, but their disputes never escalated beyond shouting, neighbors said. Sanborn, some said, had been depressed for the last year over the death of an older brother, who was killed in a military training exercise.

Times staff writer Peggy Lee contributed to this story