Joey Massino's testimony is on the Black Hand forum. Massino said Bonventre was shaking down drug dealers. He beat one dealer, Anthony Aiello, out of 5 or $600,000. Bonventre took 10 or 15 kilos off him and never paid him. But Aiello was around Phil Rastelli. So Rastelli called Bonventre in and questions him about it. Bonventre denied everything, got insulted and walked out of the meeting. Because of this disrespect, Rastelli ordered him killed.

My guess is Bonventre had just become so full of himself and didn't respect Rastelli's authority given the tumultuous past few years.