(e) With respect to property other than a dwelling, curtilage, or an occupied motor vehicle, a person is justified in using reasonable force against any other person if the person reasonably believes that the force is necessary to immediately prevent or terminate the other person's trespass on or criminal interference with property lawfully in the person's possession, lawfully in possession of a member of the person's immediate family, or belonging to a person whose property the person has authority to protect.The op did almost NOTHING right!
first, he let his girlfriend answer the door! WTH?!
then he pointed a gun at the guy, and possibly (probably) his girlfriend too!
how do you figure he felt threatened? Because the guy had his hand in his pocket and was crying?