If you happen to be in sporting goods grab a can of Coleman fuel and a torch, douse the floor and light it up so the sprinklers go off and soak the store, then shooter will slip and fall on the slippery tile and drop the heater, which you can then grab and blast him. For best results, apply directly to the forehead.
18 yrs ago when I fitst started, I casually walked the store when I could my first week there, noted all the emergency exit doors, then planned how I'd get the hell out of Dodge at a seconds notice incase of robbery or worse.