How do I handle a suicidal person???

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I really do not know what to do because my friend is a very sensitive person and wants to suicide. He just doesn't want to live anymore he says that our world is corrupt with so much anger, crime, and war and it is a planet that he no longer can stand. I really don't know what to tell him everytime I'm around him I have to watch what I say. Still I do not want him to kill himself because I know that he is willing to he even has a date for his planned suicide because I was digging around his room while he went to get snacks. That's where I saw it a calender with the date of his suicide and it's really sad maybe I should tell his parents or call the police or something, but I don't know. I don't know why he regrets his life so much he shouldn't be sad he should cheer up I know I;m asking to much there, but hes my friend and I care about him so.