The first fatal Autopilot accident occurred on May 7th 2016
According to Tesla's statement, the Model S was driving down a divided highway when a tractor trailer cut across the highway perpendicular to the vehicle.
"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,"
Tesla said in its blog post.