A woman in Tempe, AZ was killed after she was struck by a self-driving Uber car. This is the first reported death of a pedestrian killed by an autonomous car.

The car was in autonomous mode and had a safety test driver in the driver’s seat. The victim was walking across a crosswalk around 10 p.m. when she was killed. In response to the accident, Uber suspended the testing of their self-driving cars in other cities.

“Our hearts go out to the victim’s family. We are fully cooperating with local authorities in their investigation of this incident,” said an Uber spokeswoman, Sarah Abboud, according to a New York Times article.

This unprecedented accident will force companies and the government to consider what regulations should be placed on the testing of self-driving cars. Currently testing is allowed for cars that have a human driver in case of an error, but California said that it would soon be allowing companies to test the vehicles without their human counterparts.

“It’s possible that Uber’s automated driving system did not detect the pedestrian, did not classify her as a pedestrian, or did not predict her departure from the median,” said Brian Walker Smith, a law professor at the University of South Carolina who has studied autonomous vehicle liability in a Bloomberg article.

Self-driving cars are expected to become one of the safest modes of transportation, as they remove human liability from the equation of driving. But until developers are able to respond to sporadic human behavior or unpredictable events on the road, self-driving cars will remain a concept of the future.