If you own a store and are getting robbed, you have a few options. Even if you have a gun, you need to wait until they are distracted. The easiest way is by filling the money into a bag with a hole. As soon as money falls out and they look down, grab your weapon and open fire. Do a full mag dump just to be sure. If they're still moving, reload and shoot their hands to make sure they can't try anything suspicious.