several theories behind who killed him

1) Genovese family are the most likely he was a junkie and causing them problems embarrassing them by fighting made guys like dom cicale in the Bonanno family (another junkie and rat). Some believe that his own father had him killed or at least had knowledge it was going to happen after the feds tried to question him about his sons disappearance he refused to answer questions

2) He got in a fight with dom cicale there was rumours it was the Bonannos but vinny basancio on tape told joey Massimo that they had nothing to do with it. A lot of people believe it was dom cicale who killed him on the sneak and never told the feds or they covered it up for him