I have thought about this matter during the day, wondering what course of action I would take now if the same situation were repeated again.
What I would do is address the shop staff member " Excuse me, but I didn't see you check this customers firearm is empty and safe" " Do you consider that this firearm is pointed in a safe direction"? I think that putting the responsibility on the shop staff is going to cause less of a situation than bailing up a customer. The shop staff being put on the 'back foot' whereas the customer is very likely to be defensive and offer two words in response.
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