A guy I used to be friends with slowly went crazy, having paranoid delusions about space lizards and people conspiring against him. He couldn't be reasoned with, he wouldn't see a psychiatrist, and he just became an intolerable basket case and scared off everyone in his life. His family and some of his closer friends tried to get help for him because there was a very real possibility that he could harm someone, including himself.
The most they could do was get someone to make a record of their concerns.
This fall, he went out west and jumped in front of a train.
The mental health resources were all there, but it ultimately makes no difference.

Having to deal with people doing crazy shit sometimes is the price we pay for having the freedom to live our own private lives, and I can live with that. More kids drown in swimming pools than get shot dead my maniacs, after all, and and nobody seems to feel that it's too high a price to pay for the luxury of having a pool.