A couple of months ago, news broke that Uber would be testing their first run of self-driving cars in Pittsburgh. That definitely sounds cool and futuristic in theory, but with such developments in technology come safety concerns.

Those very concerns were realized when an Arizona woman was struck by a self-driving Uber car on late Sunday or early Monday. The woman died from the accident, according to the New York Times. Tempe, Arizona police confirmed that the car was in autonomous mode with a human safety driver when it hit the female pedestrian — who has not been publicly identified — as she crossed the street outside of the crosswalk.

“The vehicle was traveling northbound just south of Curry Road when a female walking outside of the crosswalk crossed the road from west to east when she was struck by the Uber vehicle,” the said Tempe police in a statement according to CNET. “She was transported to a local area hospital where she passed away from her injuries.”

Uber CEO Dara Khosrowshahi tweeted out his condolences on Monday, following the tragic incident.

According to USA TODAY, this may be the first death related to a self-driving car. Self-driving cars are often promoted as a way to reduce traffic related pedestrian deaths. Last year, 40,000 people were killed in relation to traffic accidents.

A spokeswoman for Uber confirmed that the ride share company is “fully cooperating” with local authorities. Furthermore, Uber has suspended its self-driving car tests in Tempe, Pittsburgh, San Francisco and Toronto.