this guy wants to kill him self!!

so I have a boyfriend and I love him a lot right… ok bottom line im happy with my love life and wouldnt want it any other way… there is a guy though who is madly in love with me and doesnt leave me alone. He knows I have a boyfriend but he still chases me. He calls me at least 20 times a day but I dont pick up- leaves me like 100 voicemails.,, I changed my number but he still got it… hes a gangster type of a guy and he honestly has no life. he called me the other day and I picked up to tell him to f^^^ off and he was crying tellin me he was gonna commit suicide. I didnt believe him but he was talkin crazy and he would do it… he told me he has nothing to live for exept me and if I dont give him a chance to be with me hes gonna kill himself at the end of the week. I believe he will because he is a disturbed guy that is hated by his family and everyone… but hes a good guy good looking and good hearted… WHAT SHOULD I DO?? I dont want to be with him but I dont want him to kill hisself so pleasee help me because if nething happens im gonna blame myself… what can I say to him or what can I do? and btw my boyfriend doesnt no about this or he would kill him…

pleaseee helppp thank youuu