User blog comment:CrashingCymbal/Are There Any Serial Killers/Murder Cases That You Have a Keen Interest In?/@comment-24077689-20140129160714/@comment-5269370-20140129224833

Indeed. He used killing as a way of ventilating the trauma caused by his terrible childhood, as his first "killing" was actually an accident (so manslaughter), but it gave him a rush like he'd never experienced before which just grew out of control.

I could never quite explain the Bozo the Clown persona, but you've probably hit the nail on the head with him contacting his lost childhood innocence. That part of Gacy has always been disturbing, yet fascinating to me.