A man is suspected of firing a shotgun at a toll booth near a heavily traveled bridge north of San Francisco, killing a toll collector and one other person and leaving a gruesome scene that snarled Tuesday evening commuter traffic, the California Highway Patrol said.

Authorities are looking for a man they've identified as Nathan Burris in the killing of the toll collector — a 51-year-old Richmond woman — and a man who was sitting in a parked car at the entrance of the Richmond-San Rafael Bridge.

The shooting took place at about 6 p.m., authorities said. Burris was believed to be driving a white Ford van with "Western Express Shuttle" written on the side, Patrol Officer Sam Morgan said.

Gov. Arnold Schwarzenegger's office said the woman was Deborah Ross, who had worked as a Caltrans toll collector for eight years. Capitol flags will be flown at half-staff in her honor, a statement said.

Officers found Ross' body inside a toll booth, and investigators have been searching for clues amid shattered glass. Patrol Sgt. Trent Cross described the scene as "horrific."

The patrol was working with Richmond police and other agencies to find the gunman.

The bridge over the northern portion of San Francisco Bay connects well-to-do Marin County with Richmond and other East Bay suburbs.