Police have released footage of a self-driving car fatally hitting a pedestrian in Phoenix.
Elaine Herzberg, 49, had been wheeling a bicycle when she was hit by the Uber car, which was in autonomous mode at the time.
The footage, taken from inside the Volvo XC90, shows her walking out from a darkened area and stopping the moment before she was struck.
The vehicle had been travelling in the right-hand lane of a four-lane highway.
Ms Herzberg was not seen in the SUV's lights until a few seconds before it hit her, raising doubts over whether the vehicle would have been able to stop in time.
This is a factor investigators are likely to focus on as they examine the self-driving technology.
But they will also ask why the car's sensors did not pick up Ms Herzberg's presence, considering she had crossed three lanes of traffic before being hit.
Ms Herzberg's death is the first involving a pedestrian and an autonomous vehicle.
The video also shows the car's operator, Rafael Vasquez, looking down before the collision, only looking up a few moments before the impact.
Uber said: "The video is disturbing and heartbreaking to watch, and our thoughts continue to be with Elaine's loved ones.
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"Our cars remain grounded, and we're assisting local, state and federal authorities in any way we can."
The ride-hailing firm had been testing the self-driving vehicles in Tempe and Phoenix for months.