Don't go out to the car. If you think someone is breaking into it, call the police. If you go outside and someone is breaking in and it catches you off-guard, get back indoors and call the police. A car is not worth shooting someone over in my opinion. You have insurance that will cover damages/loss if you have a police report. Shooting someone can bring down the fires of hell and is not worth doing unless death or serious injury is on the line.