Federal officials say the driver of a Tesla S sports car using the vehicle's "autopilot" automated driving system has been killed in a collision with a truck, the first U.S. car fatality involving such a system.

The National Highway Traffic Safety Administration says preliminary reports indicate the crash occurred when a tractor-trailer rig made a left turn in front of the Tesla at a highway intersection.

NHTSA says the Tesla driver died due to injuries sustained in the crash, which took place on May 7 in Williston, Florida.

Tesla Motors issued a statement on its website Thursday, calling the death a "tragic loss." The crash happened under "rare circumstances," in which the tractor-trailer collided with the car from above, impacting it through the Model S's windshield. The statement continued:

Neither Autopilot nor the driver noticed the white side of the tractor trailer against a brightly lit sky, so the brake was not applied. The high ride height of the trailer combined with its positioning across the road and the extremely rare circumstances of the impact caused the Model S to pass under the trailer, with the bottom of the trailer impacting the windshield of the Model S.

Had the impact occurred at the front or rear of the trailer, it's likely Tesla's safety system would likely have prevented the crash, the company said.

Tesla Motors also emphasized that the autopilot mode is an "assist" feature that still requires drivers' attention:

When drivers activate Autopilot, the acknowledgment box explains, among other things, that Autopilot “is an assist feature that requires you to keep your hands on the steering wheel at all times," and that "you need to maintain control and responsibility for your vehicle” while using it. Additionally, every time that Autopilot is engaged, the car reminds the driver to “Always keep your hands on the wheel. Be prepared to take over at any time.” The system also makes frequent checks to ensure that the driver's hands remain on the wheel and provides visual and audible alerts if hands-on is not detected. It then gradually slows down the car until hands-on is detected again.

The driver's identity has not been disclosed, but Tesla said he "was a friend to Tesla and the broader EV community, a person who spent his life focused on innovation and the promise of technology and who believed strongly in Tesla’s mission."