Well, it wasn't a Thompson...
When I was 12 years old, my Mom and I found a sawed off single shot 12 gauge and a white canvas bank bag on the side of SR 180. The bag had the name of some bank from Kentucky IIRC. (there was no money in the bag) We took it to the Sheriff's dept. and Mom filed a report.
Stopping power: The power some guns have to make you stop what you are doing and get your wallet out.