Someone tried to break my parents car window while she was driving!!?

First, side windows are very strong and the curvature of the glass is the reason for that, a curve creates strength, you often have to use hard force or a blunt heavy object to break a window. Two - She should absolutely report it to the police - some nut is running around assaulting vehicles - he's a danger, and the police should know about it. Three - if you are in danger you need to do what you can to protect yourself, whatever it is, even breaking the law - protect yourself first. Yes, the car who backed out saw what was coming and moved out of range. AND always, always, always keep all your doors locked no matter what time of day or night.