Two self-driving car companies in Boston have agreed to suspend testing in light of Sunday’s fatality in Arizona, where a self-driving Uber car killed a pedestrian.

NuTonomy and Optimus Ride have tested self-driving vehicles in the Raymond L. Flynn Marine Park as well as the Seaport. The two suspended their testing after Boston Mayor Martin Walsh called for a hiatus Monday, the Boston Herald reports.

“None of us really know what the future of autonomous vehicles are,” Walsh said to the Herald. “I think this is a long discussion that’s going to continue to happen. There’s going to be other incidents that I think will happen as we move forward here, but I think it’s how do you come up with a system that’s as close to perfect as possible.”

Optimus and nuTonomy have driven nearly 1,000 miles combined in Boston without a crash, according to city documents. While testing began in the Flynn Marine Park, it expanded to general Seaport streets, where nuTonomy carried passengers for Lyft with operators behind the wheel for added safety.

Aptiv, which acquired nuTonomy in October for $450M, announced in December it was opening a 300-person office in the Seaport on Northern Avenue.

Arizona Police reported Elaine Herzberg was crossing a road without a crosswalk when an Uber car operating in self-driving mode with a safety driver struck and killed her. While an investigation into the crash is ongoing, Uber suspended self-driving tests in Arizona, Pittsburgh and San Francisco.