FILE - In this Dec. 13, 2016 file photo, an Uber driverless car waits in traffic during a test drive in San Francisco.
Eric Risberg, AP

PHOENIX — A fatal crash involving a self-driving Uber likely was "unavoidable" based on an initial police investigation and a review of video, Tempe Police Chief Sylvia Moir told The Arizona Republic on Tuesday.

Moir said, however, that any charging decision would be up to the Maricopa County Attorney's Office. 

The accident is believed to be the nation's first pedestrian death involving an autonomous vehicle. 

Elaine Herzberg, 49, of Mesa, was walking a bike across a busy street outside any crosswalk near the Marquee Theatre in Tempe at about 10 p.m. Sunday when she was hit, police said. She died of her injuries.

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The car, a Volvo operated by San Francisco-based Uber, was in autonomous mode when it hit Herzberg, police said. Uber has not disputed the official narrative from police.

The vehicle had a backup operator behind the wheel, which is common in case the vehicle has to be taken out of self-driving mode. Officials identified the operator as 44-year-old Rafaela Vasquez.

At a news conference Monday, Sgt. Ronald Elcock, Tempe police spokesman, said impairment didn't appear to be a factor for Vasquez or Herzberg. 

Police have said the Volvo had a video camera that recorded the crash. The Volvo was traveling about 40 mph and made no visible attempt to brake in the video, Elcock said.

The speed limit in the area is 35 mph. 

"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 told the San Francisco Chronicle after viewing the footage.

A large median at the site of the crash has signs warning people not to cross mid-block and to use the crosswalk. But the median also has a brick pathway cutting through the desert landscaping that accommodates people who do cross at that site.

Stephanie Sedlak, a spokeswoman for Uber, said the company is aware of Moir's comments but it would not have any comment until a full investigation is done.

"We're waiting for the results of the investigation," she said.

The National Transportation Safety Board is also part of the investigation. The agency said in a statement that a team of four investigators will go through Uber's equipment and video to help determine what caused the crash, in addition to looking at "the vehicle’s interaction with the environment, other vehicles and vulnerable road users, such as pedestrians and bicyclists." Human performance also will be examined.

Amanda Jacinto, a spokeswoman for the Maricopa County Attorney's Office, said that when Tempe police finish the investigation, a prosecutor will review the case to determine if charges should be filed. 

"We will assist as needed and await a submittal to conduct a charging review, if appropriate," Jacinto said.

She added, "Not all vehicular incidents, even those that result in the tragic loss of life, ultimately present a case for a criminal prosecution."

A year ago, a vehicle struck a self-driving Uber SUV in Tempe. In that case, police found the driver of the other vehicle at fault and said the Uber car was obeying the law.

Uber has been carrying customers in the self-driving cars in limited parts of Tempe and Scottsdale, in addition to other locations in North America.

The company on Monday paused its self-driving car operations in the Phoenix area, as well as in San Francisco, Pittsburgh and Toronto.