Sunday marked a turning point for self-driving cars. For the first time, a car in full autonomous mode struck and killed a pedestrian.

It happened at 10 p.m. in Tempe, Arizona, where ride-hailing company Uber had been picking up passengers in autonomous vehicles for more than a year.

Elaine Herzberg, 49, was walking her bicycle down a four-lane road and was starting to cross when the gray Volvo, operated by Uber, hit her at about 40 mph, according to local police. It's believed Herzberg was homeless. She was pronounced dead by the time she reached the hospital.

Although the car was driving itself, Uber vehicle operator Rafaela Vasquez, 44, was behind the wheel.

"Our investigation did not show at this time that there were significant signs of the vehicle slowing down," Tempe Police Sgt. Roland Elcock said in a press conference Monday. The police are "going to attempt to find who was at fault and how we can better be safe," he added.

The Tempe police on Wednesday released a video of the collision. It shows footage of Herzberg crossing the road outside the vehicle and of Vasquez at the moment of impact. It's graphic and difficult to watch. 

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