Transcript for 'My Father BTK' - a 2-Hour 20/20 Documentary Event Special - Tonight at 9/8c on ABC

As a result BGJ strain your critique it was a monster who killed him Cole was. We were all scared about general C a funerals going to challenge it. Nobody would have imagined this good husband. Somebody that's even contemplate the murders that you. News Obama. My father's a good guy boy scout leader president of the church. And then there's a knock at my door. Asked to your nose movie TK as I was like you mean that person is wanted for murder and knees as your dad has been arrested as DT tank. I was lying. I think when a pass out. Painting he was. As the boogie man made real. He would see a woman walking they would look at her and he would say. She's did he would break into someone's home hide in claws and wait how wars until they were fast asleep and then attacked. To this day. I still check in tight the closet under the bed behind the shower curtain here. Children's efficiently. The men stopped just look upon without police are investigating the possible return of us your real killer when BTK came forward. Everybody's life changed she said he wanted to be the most famous serial killer country serial killers don't quit killing him towards. He felt it necessary. To contact law enforcement saying no I'm still here in one instance he left the cereal box on a county road. Cereal boxes because serial killers cereal boxes that this is great joke this is what it called this cat and mouse game. Was I don't even expect from it scares me the Al by myself in line just unbelievable and totally in disbelief. Your. Father is confessing to being a serial killer now my guide and there really as my father. If his family had no idea what he was up to it really makes you question how well do you know anything. He terrify entire city shocked the nation now the daughter of one of America's most notorious serial. Finally free exercise its what does she now reveal about. PTK. 20/20. Friday night a special time. I need central and. You call.

This transcript has been automatically generated and may not be 100% accurate.