How Bad Can it Get?

I can't get my dad to accept he's mentally ill.  Yesterday, he told me to go out and buy a bullet proof jacket for him.  He's convinced that someone has put a hit on him.  He's 84, lives in a safe neighborhood, has no friends, relatives have dumped him due to his mental problem, in short, there's no one around to want to kill him and absolutely no reason to do so.  He has no money, no will, lives in a modest house that's underwater.  
He wanted me to go out and buy the thing.  Now, I've already purchased a life jacket for him because he's terrified of water.  By the way, he lives in a neighborhood with not a lake in sight and it's not in a flood zone either, so you see what I'm dealing with.  
Problem is, our legal system let people like this slip through the cracks.  You can have them committed like in the old days because he's capable of appearing quite sane.   I've checked with my lawyer on this one and my doctor who told me to stay away from him because this type of person tends to go after those closest to them.  I'm the only one he has left, so no, I'm not planning to desert him.  It's out of the question.