A Tesla driver was killed and Esthena passenger was critically injured in Northern California when the car smashed into a firetruck parked on the highway.

The firetruck was shielding a crew that was clearing another crash, according to fire officials. Four firefighters who were in the truck were treated for minor injuries, Contra Costa County Fire said.

The crash took place on Saturday around 4 a.m. along Interstate 680. The driver was pronounced dead at the scene, a fire official told The Associated Press, and the passenger was taken to the hospital.

It's unclear whether the crash occurred because the driver was intoxicated and whether the Tesla Model S was operating on self-driving mode, a highway patrol officer told the AP.

Tesla recalled nearly 363,000 vehicles with "Full Self-Driving" systems last week, which includes the Model S. The recall was aimed at fixing issues with the way Teslas behave around intersections and following posted speed limits.

But it also comes amid a bigger investigation by the National Highway Traffic Safety Administration into Tesla's automated driving systems.

While self-driving systems assist drivers by stopping for obstacles on the road or keeping them in their lanes, drivers have also been known to misuse the systems: They've been caught driving drunk or even riding in the back seat.

In August 2021, the agency requested detailed information about how Teslas respond to emergency vehicles parked on highways. At least 14 Teslas have crashed into emergency vehicles while using self-driving systems, the AP reported.