Prohibition was a brutal era. I would not be surprised if political shipments were not enough to keep Costello liquor protected. Would not be surprised if he (partners with Joe Kennedy) had a few 1920's notches on his killing belt. Murders Ordered, however: Abe Reles

Bonanno? Perhaps in Sicily. Not in America. His first two Consiglieres were brutally murdered, however.

I don't believe Gambino ever killed someone. It was a widespread rumor. He and Paul never made their bones.