I don't know about the USA since I don't live there, but when a patient expresses a serious wish to do harm to themselves or others, don't doctors have a responsibility regarding that anyway? (eg. involuntary admission in the case of the former, not sure about the latter, if it's not involuntary admission it's maybe to tell police of the realistic threat?)

So in this case wouldn't it be similar, ie. recognising whether the person might follow through on certain comments/wishes? Or maybe at worst, if someone has an ongoing, serious anger problem and has a history of violence, then they'd need to say something about that patient so they don't get sold a gun/keep the one(s) they already have? Seems sensible enough to me