FLORIDA – Tesla Motors on Thursday disclosed the first known death caused by a self-driving car, casting doubt over the revolutionary self-driving car technology.

According to reports, the accident occurred on a divided highway in central Florida on May 7 when a tractor trailer drove across the highway perpendicular to the Model S. Neither the driver, nor the car noticed the big rig or the trailer “against a brightly lit sky” and brakes were not applied.

The incident left 40-year-old Joshua Brown dead but the driver of the truck remained safe. He claimed that the deceased Tesla driver was watching Harry Potter at the time of accident.

The owner Tesla Motors, Elon Musk took to Twitter to condole with the family of Brown.

Earlier, Joshua Brown posted a video in April which showed him narrowly escape an accident on the highway thanks to his Tesla’s autopilot feature.

The National Highway Transportation Safety Administration (NHTSA) is now investigating the incident.