whether it's common or not is irrelevant, if what he was doing was legal and within his rights then that is that case closed.
Of course it's relevant. It's the determining factor as to whether people justifiably felt threatened which is the basis of whether he broke a law or not. Imagine if everyone in Walmart wore combat armour and carried a gun. If someone walked in who also wore combat armour and carried a gun, I imagine no one would bat an eye. In which case, he wouldn't have broken any law.
I take it from your reaction that no, this is not the case. It is indeed threatening for most people when someone walks into walmart wearing combat armour and carrying a gun. Hence, case closed. People were justifiably threatened and what he did was against that particular law.
does anyone who carries a gun give you the prospect of being shot? if not does it depend on what they look like? or what is the criteria we should go by?
I mean an obvious criteria is setting. If I were at a gun show, I would expect to see people carrying guns around. Combat armour might be a bit excessive sure but I probably wouldn't notice it too much.
Now at the opposite end of the spectrum, if I were chaperoning at a childrens party I would be extremely concerned if I saw a person walk into the event wearing a combat vest and carrying a gun because that person invariably is there to cause either panic or harm.