Public health officials can override HIPAA in the event of a threat to public safety. This was meant to stop infectious disease spread but the verbiage is loose for a reason. The legislation is there, now how do you implement it. I would call this a public safety issue for sure. It is going to be tough to say who can and who can't purchase a gun. Claustrophobia and social anxiety are mental illnesses. Does Billy's fear of giving speeches mean he shouldn't be able to buy a gun?
It is a tough thing to work through for sure.
I think linking mental health with buying a gun would be a waste of time. This latest kid didn't buy any of his guns, last I heard they were his moms. I'm afraid the only answer will be to make more help available, less stigmatized, and more affordable as well.