A Tesla with its 'Autopilot' mode activated collided with a truck, shearing the roof off the car and killing the Tesla driver. 

40-year-old Tesla owner Joshua Brown's Tesla Model S failed to recognise a white tractor-trailer crossing its path against a bright sky on a highway outside Williston, Florida. The car passed under the trailer, shearing off its roof and resulting in Brown's death due to head injuries. 

The Autopilot system did not apply the brakes, and Brown did not take evasive action in the final seconds before the crash.

Tesla responded to the incident stating that its Autopilot driver assistance system had been engaged but may not have functioned properly as it had failed to isolate the image of the tractor-trailer from the sky behind it. 

They added that the system was still in its introduction phase and had limits, and suggested drivers always stay alert with their hands on the wheel while using it.

Findings (pdf) from a NHTSA preliminary investigation found that Autopilot had worked as intended. 'NHTSA’s examination did not identify any defects in design or performance of the AEB (Automatice Emergency Braking) or Autopilot systems of the subject vehicles nor any incidents in which the systems did not perform as designed,' the report said.

An NTSB report had concluded that the accident should never had happened, Autopilot was partly to blame, and that Tesla 'lacked understanding' of the semi-autonomous Autopilot's limitations. 

It also found that Brown had his hands on the wheel for 25 seconds when he was supposed to do so for 37 minutes, Autopilot mode had remained on during most of his trip, and that it gave him to a visual warning seven separate times that said 'Hands Required Not Detected.' 

In addition, the NTSB said initial media reports suggesting Brown may have been watching a video were wrong. Reports also suggested Brown's family may have come to a settlement with Tesla, though neither party have confirmed this to be the case.