You'll find this post in several spots on the site- I repeat it every time I hear of one of these situations.
Some years back, my uncle bought a used car. Looked nice on the outside but once he got it home, he noticed some things. Took it to a local shop and discovered that it was a rebuilt wreck. Obviously upset, he called the seller and demanded a refund. The seller was accomodating on the phone. They decided to meet later that day and un-do the transaction. Since he needed a ride back, my cousin (not his son, his wife's sister's kid) followed him out. My cousin is a little unstable- another story altogether. Anyway, the guy gave him the money and go the car back. But he was short a few hundred- told my uncle that was all he had and would make it up later. Before my uncle could say anything my nutty cousin pulls a pistol and hits the guy, then holds him down and tells him the money needs to show up now. Of course my uncle had no idea this woas going to happen. At any rate, they got in the car and went home. An hour or so later, the police arrived at his house, forced entry and arrested him for armed robbery. Cousin too. Cousin got 4 years, served 2.5. my uncle got off after dropping about 50 grand on lawyers.