SAN DIEGO -- Authorities remained on the lookout Wednesday for a motorist who opened fire during an apparent road-rage dispute on Interstate 8 in Mission Valley, seriously wounding a passenger in another vehicle.

The shooting, which occurred in the westbound lanes of the freeway early Tuesday afternoon, left the 22-year-old victim with a bullet lodged in his face, according to the California Highway Patrol.

The Julian resident was in serious but stable condition at UCSD Medical Center in Hillcrest, where he was expected to undergo surgery Wednesday to have the slug near his eye removed, CHP Officer Marc Hale said.

The vehicle-to-vehicle gunfire apparently erupted after one of the drivers cut the other off, prompting glares and horn-honking between the two, Hale said.

The shooter, a Latino who was driving a silver Chrysler 300 sedan with tinted windows, evidently opened fire on the red Toyota Tacoma as he took the Morena Boulevard exit, near Interstate 5, shortly before 12:30 p.m., according to Hale.

The bullet smashed through the rear passenger-side window of the truck and hit the victim on the side of the head. The driver got off on a nearby exit, pulled into a parking lot outside a Jack-In-The-Box restaurant on Camino del Rio West, ran inside and asked someone to make an emergency call.

Medics arrived to find the victim bloodied but conscious and alert. He and his companion were unsure if the assailant had shot at them or thrown some type of projectile, possibly a rock, at the truck.

About 20 minutes after the shooting, San Diego police pulled over a vehicle matching the one driven by the gunman, but it turned out to be the wrong one, the CHP officer said.

Besides the make, model and color of the car the shooter was driving, the only detail the victims could provide about it was that its license-plate number began with the numeral "5," Hale said.

Authorities urged anyone with information about the incident to call the Highway Patrol's San Diego office at 619-220-5492.