In most states I think there are laws that allow a home owner to the right of self defense and if a person breaks into their house or enters their property lines and the owner feels reasonably threatened they have the right to defend themselves with lethal force if need be.
If a intruder gets themselves killed while invading another persons private property or business, the courts will decide if self defense was warranted. A person fearing for their family or themselves do not have to wait for the criminal to shoot at them first. That's what investigations are all about. And the homeowner is almost always incarcerated until proven innocent.
If people are going to act like that kid at the car dealer, then that wouldn't be covered by any law. But, no one had the right to be on the property either. Not getting into that case at all.