The guy in the cart screwed up. He didn't start it but he provoked a reaction. What is the loss of a radio compared to your safety. I would have just driven off, let them have the radio and collected license plates as they left. Or better yet, leave the lot as soon as you see a potential problem.

Even if you had a 12 gauge handy, and felt obligated to vaporize the leader, with that many assailants, you could end up quite dead by your own weapon......