If a store simply chooses to prohibit firearms from their store "because" I will either not do any business with them, or do as little as possible with them. If they had a shooting, accidental or other, I can respect that decision and continue to shop there.
If there had been a shooting there, wouldn't that be more of an indication that you should
And if it was "accidental"... what does the fact that somebody else misused a firearm have to do with me and my sidearm???