Slow down and move over is the message that authorities are trying to get out after another fatal crash with an emergency vehicle on the highway. The driver involved was piloting a Tesla Model S which has led some to question if Autopilot or Full Self-Driving was engaged. Authorities say that it’s too early to tell.

The driver struck a parked fire truck on the highway around 4 a.m. Saturday morning. They were pronounced dead on the scene while a passenger in the Tesla was extricated from the vehicle and taken to the hospital with major injuries. Four firefighters were aboard the fire truck at the time of the incident but all escaped without significant injury.

Authorities say that the car struck the truck on I-680 but that the cause was yet unknown. Specifically, the California Highway Patrol – Contra Costa division said on its Facebook page that it doesn’t know if “drug or alcohol influence is a factor” in the crash. At the same time, it hasn’t been able to determine if the driver was using any sort of autonomous driving aid like Autopilot or Full Self-Driving.

More: Tesla Recalls 363k Cars Over Full Self-Driving Beta’s Potential To Cause A Crash

Notably, more than 360 thousand Teslas with Full Self-Driving were recalled last week over dangers that the NHTSA says could cause an accident. Tesla vehicles utilizing such autonomous driving features have, in the past, gained a bit of a reputation regarding how they handle parked emergency vehicles. At the same time, Tesla drivers must agree that it’s up to them to avoid such accidents to use Autopilot or Full Self-Driving.

Additionally, it’s worth noting that hitting such vehicles is a major problem that more often than not has nothing to do with a Tesla. Last October, the NHTSA launched a “Slow Down Move Over” campaign to remind drivers of laws requiring them to do just that when an emergency vehicle is present.

For their part, the firefighters set a great example. While evacuating a stalled vehicle on the side of the highway is certainly the safest course of action, it’s not always practical. In this case, all four firefighters had their seat belts on before the accident. According to the CHP, they “were taken to the hospital for precautionary measures” only.

CHP is asking anyone who witnessed the crash or the events leading up to it to call 925-646-4980.

Image Credit: Contra Costa County Fire Protection District