James W. Gacy is a removed character from Manhunt. He was supposed to be the head of city's art galleries and museums of Carcer City as well some kind of "sponsor" of The Clowns. It's unknown if Gacy was meant to appear in person at any point of the game's development.
Since the Clowns have been scrapped from the final version of the game, Gacy is neither seen or mentioned other than in the art gallery. It's possible that Gacy still somewhat exists in the Manhunt universe, as Carcer City has at least one museum.