get adults (doctors) involved but don't tell him. you don't want to feel responsible if something happens
sadly people threaten to kill themselves to try and get attention to see if people care about them. show a lot of compassion and try to be with him all the time. chances are if he keeps threatening and sets a date he probably is not too serious about actually following through
"I think you have an extra chromosome lying around somewhere..."-KaDONK.
RIP Shane, you will be missed