It really depends on a number of factors, and myself is mostly right, although different jurisdictions do not require two psychiatrists. In fact, I've never seen the requirement for more than one... (Just a note. Otherwise, the 72 hour/14 day holds are the same here.)

If this is someone already seeing a pdoc or therapist, you can try to contact them. Neither will be able to talk TO you, but they can listen to your concerns. If you go this route, be specific: "he's delusional" isn't likely to get very far, but "he believes that I am leading a conspiracy against him and is therefore holding a gun when he calls me" will.

If this individual is not in treatment of any sort, then you're in a pickle -- call the police? Or not? That's really all I can suggest, and then you have to hope that the police actually take him to the psychiatric ER, and then that the PER sees that there's a problem. Some people present so well, even in psychosis, that they won't get help that way unless they're really in bad shape.

As for you, I guess I'd think validating the feelings, without validating the beliefs? You know, "It must be very frightening to you to believe that. I don't think those beliefs are accurate, though." And I'd probably add in a few concrete reasons that they're not accurate.

Good luck.