I won't be cynical and suggest that it was *not* an accident. So he had to back up, perhaps he didn't even realize until after he backed up that she was under there. Who cares if they were yelling at the driver, I'm sure that's not rare when they are protesting what the drivers are doing. If she was sitting down, maybe he *didn't* see her. It's best to be standing up and visible when dealing with vehicles.
I'm not feeling sorry for the girl too much though. It's just a crying shame that these people feel they have to die to prevent others from defending themselves. Weird.
Looks like this time it did.
Stay safe; stay armed,
Eaker