This week, a self-driving SUV operated by Uber—and with an emergency backup driver behind the wheel—struck and killed a 49-year-old pedestrian as she walked her bicycle across a street in Tempe, Arizona. It is believed to be the first pedestrian death associated with self-driving technology.

In addition to the Tempe Police Department, the National Transportation Safety Board said it was sending a team of four investigators to determine “the vehicle’s interaction with the environment, other vehicles and vulnerable road users such as pedestrians and bicyclists.” Data from the vehicle’s many cameras and sensors will no doubt prove useful to the investigations.

Uber and other tech companies and automakers have recently begun to expand testing of their self-driving vehicles in cities across the country. The companies believe that the cars will be safer than regular cars because they take easily distracted human drivers out of the equation. But self-driving technology is still only about a decade old, and we are just now starting to see the unpredictable situations that such vehicles can face.

There’s an ongoing debate about legal liability when it comes to accidents where a self-driving vehicle harms someone else through no fault of that person. Would the blame lie with the self-driving car’s manufacturer, owner, a combination of the two, or someone else? In their quest to become the epicenter of self-driving cars, Arizona regulators have largely left those questions unanswered.

Currently, product liability law offers the best guidance for determining legal fault with an emerging technology like self-driving cars.