A Tesla Semi was involved in a grisly crash earlier this week with two passenger vehicles that killed a married couple and left another person critically injured.

It’s the first known fatal collision for the battery-powered electric truck, Electrek reports. According to the Nevada Highway Patrol, the crash occurred on Sunday morning on US 50 in Dayton. The couple, identified in The Record-Courier as Sergio and Jennifer Villanueva, were stopped at a traffic signal in their Volkswagen Beetle when the semi slammed into their car, and another, from behind.

Both were pronounced dead at the scene, the highway patrol said, with a third victim flown to a hospital with life-threatening injuries.

The Lyon County Sheriff’s Office said that the driver of the Tesla Semi, whose identity has not been shared, may have fallen asleep at the wheel before the crash, based on statements taken at the scene of the accident.

Authorities didn’t specify the operator and make of the truck, but photos of the scene clearly show a Tesla Semi, making this the first known fatal crash involving the experimental tractor that CEO Elon Musk envisions as one day being able to drive itself. 

Self-driving features don’t appear to be involved in this crash, though a Tesla Semi equipped with the automaker’s Full Self-Driving hardware was recently spotted in California.

The accident does raise questions about the truck’s safety systems. As Electrek notes, Tesla originally boasted that the Semi comes with Enhanced Autopilot, an older version of its driver assistance software, and is equipped with the same cameras and hardware that allow its passenger vehicles to run Automatic Emergency Braking, a feature that’s supposed to stop the vehicle for obstacles. Still, we don’t know the exact safety features the Semis come with, because Tesla has never published them.

It’s also worth noting that Tesla already has a system for detecting driver drowsiness using cabin-facing cameras in its passenger cars. But again, we don’t know if the Semi used some form of it, as a lot of its specifications remain opaque.

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