Investigators say the shooting happened on Highway 99 near Manning Avenue just before 6:30 pm on Wednesday.
A bullet hit the driver-side window of an SUV, but no one was injured.
The driver immediately pulled over at a nearby gas station to call for help.
Officers say that's exactly what any driver should do if they find themselves in a road rage incident.
"Best advice is to pull off the road where its safe exit the freeway and get on the phone, call 911 and give as much information as you can of that suspect vehicle," said CHP Officer Mike Salas.
Anyone who may have witnessed the shooting is asked to contact the California Highway Patrol.