green was going to beef with anybody who had some power. greene thought since John Nardi was on his side that tony milano (nardi's uncle) was going to protect him. milano died in 1978 and was failing by late 1976. greene was a dead man to start with, there was no one incident that caused his death. check this out

http://clevelandmagazine.com/ME2/dirmod.asp?type=Publishing&mod=Publications%3A%3AArticle&mid=1578600D80804596A222593669321019&tier=4&id=DF84DD6073D84C4DB49BA3EDFA0AFEFF