John Kobler, in his excellent bio of Capone, implies but doesn't state that Torrio arranged the murder because Colosimo wasn't paying attention to the potential of Prohibition. Laurance Bergreen, in a later, excellent bio of Capone, says Frankie Yale did it to expand his influence in Chicago. But he never follows up on that idea.
Ntra la porta tua lu sangu � sparsu, E nun me mporta si ce muoru accisu... E s'iddu muoru e vaju mparadisu Si nun ce truovo a ttia, mancu ce trasu.