Editor’s note: Since this story was published, dashcam video from just before the accident has been released. A viewing of it offers a different perspective than that of the Tempe police chief. The video and a story about it are here.

Pushing a bicycle laden with plastic shopping bags, a woman abruptly walked from a center median into a lane of traffic and was struck by a self-driving Uber operating in autonomous mode.

“The driver said it was like a flash, the person walked out in front of them,” said Sylvia Moir, police chief in Tempe, Ariz., the location for the first pedestrian fatality involving a self-driving car. “His first alert to the collision was the sound of the collision.”

Traveling at 38 mph in a 35 mph zone on Sunday night, the Uber self-driving car made no attempt to brake, according to the Police Department’s preliminary investigation.

Elaine Herzberg, 49, was unconscious at the scene and later died of her injuries at a local hospital. At a news conference, Tempe police said it appears that she may have been homeless.

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The self-driving Volvo SUV was outfitted with at least two video cameras, one facing forward toward the street, the other focused inside the car on the driver, Moir said in an interview.

From viewing the videos, “it’s very clear it would have been difficult to avoid this collision in any kind of mode (autonomous or human-driven) based on how she came from the shadows right into the roadway,” Moir said. The police have not released the videos.

The incident happened within perhaps 100 yards of a crosswalk, Moir said. “It is dangerous to cross roadways in the evening hour when well-illuminated, managed crosswalks are available,” she said.

The Tempe police will collaborate with investigators from the National Transportation Safety Board and the National Highway Traffic Safety Administration in probing the accident.

While hundreds of autonomous cars operate in Arizona, Moir said she was aware of only one other accident, which occurred a year ago. It also involved an Uber in self-driving mode, which was flipped onto its side. But authorities determined that the other car involved was at fault for failing to yield and cited its driver for a moving violation.

“I suspect preliminarily it appears that the Uber would likely not be at fault in this accident, either,” Moir said.

However, if Uber is found responsible, that could open a legal quagmire.

“I won’t rule out the potential to file charges against the (backup driver) in the Uber vehicle,” Moir said.

But if the robot car itself were found at fault? “This is really new ground we’re venturing into,” she said.

— Carolyn Said