Butch Gilzean is the second-in-command to Fish Mooney who later becomes the second-in-command to Oswald Cobblepot.
Butch is a jovially brutal individual, happy to hand over the baseball bat to Oswald and encourage him to continue the beating others started. He appears to like Harvey Bullock on a personal level, but shares Fish’s ability to truly believe that ‘it’s only business’ when he hangs the cop up and leaves him to be filleted.
Butch is the sole survivor, from his group, of the cop killing attempt, and suitably submissive to Don Falcone, which probably explains why he’s still breathing at the end of the episode. The other examples of Fish Mooney’s henchmen are not so fortunate. He has a contempt for cops which his profession generally requires him to mask, but when ordered to take out James Gordon and Bullock, he does so with a certain relish. (Pilot)
Butch was later brainwashed by Victor Zsasz, in order for him to work for Oswald Cobblepot. (http://gotham.wikia.com/wiki/Butch_Gilzean)
Season 2 premieres 9.21.15 at 8/7c on FOX