C store clerks are told to surrender the money. It can be replaced. You have no dog in this fight. Back off to cover, escape if possible. Be a good witness from a distance. The store doesn't want your help. You could start the ball rolling and get people killed, including yourself. Some BGs can shoot quite well, and quickly.
If your life becomes threatened, then your weapon can be used.
I managed a c-store for a lot of years. Last thing I wanted was a gun fight over a corporations money.