Except it didn't immediately do that. Cruise released a report today saying that the car actually drove 20 feet and dragged the woman. There is no simple answer as to what to do. It's simply difficult and acting like there are easy answers to this is unproductive and imo not in the spirit of hackernews.
It's difficult to program an autonomous vehicle to handle this correctly, sure. That doesn't mean an average human driver wouldn't have done better. Of course a human driver wouldn't just keep driving to pull over after hitting a pedestrian and not being able to see where they went.