But what was the beef between them? Can't find anything about that online..
from everything I read,, and there is a thing or two about the incident in "five families" galente had done a long stint in prison, according to the author- galente was a big time drug dealer
and Costello, and Gambino both were against his violent ways,
so consequently galente hated them both, why he did it, I can only surmise that his mind was not functioning normally.