I would say that if that revolver was not available, the robbery would have still happened anyway, but another weapon would have been used. I saw a video where a guy robbed the convenience store with an 8 foot long stick. It's almost irrelevant what the weapon is, if somebody wants to rob someone, they're going to find a way to do it.
Also, I could be completely wrong, but it appears that revolver is a conversion. I think I can see a shiny brass cartridge in the cylinders. It looks too big to be a cap.
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It wouldn't surprise me if a few incidents like this happen, and they end up turning the conversion cylinders into FFL items.