Don't get in messes like that. Mediate from the outside. Give them a "break it up" in the harshest cop voice you can find, or pull people away from the intersection of people. Putting yourself in the middle is a bad idea. You could have easily yelled "Sheriff's Department" while pulling your buddy out. The last thing the other kid would have done is swing without knowing if he's hitting a cop or not. By the time he is sorted out and if he still chooses to chase you to the truck, you then use whatever force is needed against 5 assailants who have chased you to your vehicle to do you harm. At that point castle doctrine kicks in, and you can use deadly force. It'll probably never come to that, chances are they don't chase you out door into a vehicle, but it sure beats getting your skull caved in by a group of idiots.
