this is "nightline." >> the most infamous, unsolved serial killing spree in wichita history. >> he is one of america's most notorious serial killers. >> he calls himself the btk killer. >> it stood for bind, torture, kill. that was his m.o. >> reporter: as denis rader spends 175 years in prison for murder, his daughter opens up about being railed sed >> you realize, my god, my father's a psychopath. >> how she helped investigators unlock the mystery by providing

the missing key. plus the stunning admission. >> i still love my dad today. >> "nightline" will be right back.

"nightline" continues. here now, deborah r >> on february 25th, 2005, when i found out my father was arrested, this place became not

my home. and no one ever slept in my house again. >> he calls himself the btk strangler and promises to kill again. >> the brutal crime shocked wichita. >> the most unsolved killing spree in wichita history. >> btk stood for bind, torture, kill. that was his mchb.o. >> reporter: three letters which can touch off memories for anyone who lived in wichita in the 1970s. >> he would see a woman walking, and he would say she's next. >> one minute had a loving father. >> right. >> reporter: the next minute, he's a serial killer. i mean, come on, the child of a serial killer actually talking about it? that's something you almost never hear. kerry rawson was 26 years old on the day she learned her father

was the cold blood killer known as btk, responsible for killing ten people and terrorizing wichita, kansas for decades. >> there was a knock on the door. he said he was the fbi. he says your dad has been arrested as btk, and i'm going . >> wichita was a wonderful city back in the 1970s. just a nice, midwestern city, where people could raise their family without any fear. >> never in a million years did wichitans think that a serial killer would come from here. >> my mom and dad met in 1970. they got married nine months later in may of '71. >> reporter: while he appeared to be a happily-married man, his monstrous life would appear. >> the home of

his wife. >> he spotted her when he was driving my mom to work and stalked her family. >> reporter: he went to the house one day and cut the phone line, then killed both parents, along with their two youngest children. >> when the older children came back from school and discovered their parents. >> i ran down the hall, went in their bedroom and saw my mother on the bed, me father on the floor. my heart just got ripped out of my chest. my life changed instantly. >> 11-year-old josephine otero will be bound with rope and is hanging just off the floor. >> leaves his dna at the scene and leaves. >> reporter: police did peck up three men for the otero murders which angered raider. >> killers like denis rader are called power control killers. they love the power, they love the control and they want the attention. what's the natural way to get

attention without identifying yourself is to interact, call the media. >> reporter: raider calling the local newspaper, claiming to be btk and directing them to proof. >> this guy tells them to look in the city library, tells them a specific place, tells them the shelf and book to look for. >> the police go find the book, and there is a letter that describes the otero murders in detail. in the letter, he suggests the moniker btk, which would stand for bind, tor tuture, kill. >> reporter: he became a father and led the life of a normal family man with a job at a security company. but. >> from 1974 to 1977 he will kill three more women, a college student named kathryn brieght, mother of three named shirley and a 25-year-old named nancy

fox. >> he called in the murder of nancy fox. >> yes, you a homicide. >> the caller said, reporting a homicide. police went to that address and found nancy fox dead, bound and strangled on her bed. >> you will find a homicide. >> reporter: so, when you heard this, did it sound like your father? >> can you hear that clip, the way my father could talk. >> reporter: how would you describe your childhood with your father? >> i pretty much had the american dream, the three bedroom ranch with the big back yard and the springer spaniel dog. and then when i was 4 he built a massive treehouse for my brother and i. it was extremely out of the characteristic of my father to be physical ly abusive. >> reporter: but his murderous intent never went away. >> april 27, it's 1985, and

marine hedge, who just happened to be his neighbor, about six doors down, becomes victim number eight. >> the body was nude and police say badly decomposed. a pair of knotted pantyhose were found lying in the ditch beside it. >> over the next five years he kills two more women. vickie in september 1986 and dolores davis. >> after he married dolores davis he went silent for a long time. >> reporter: life went on for the raider family, kerry going off to college and meeting her future husband. >> he just seemed like another regular wichita dad to me. >> and then in 2003 my dad walked me down the aisle at our wedding. >> reporter: in 2004, a local paper writes an article about the 30th anniversary of the

first btk killings. >> and we include in there that nobody remembered him, which invoked his ire. >> this morning we have more information on the letter sent to the wichita eagle by the btk killer. >> btk started sending packages with mementos from his crimes. >> reporter: one of those boxes contained a floppy disc. >> we got into the meta data, and it showed that it had been typed on by a computer at a church in park city. the name of the computer was register the to the name of dennis. >> reporter: investigators found the church president was denis rader. they also had an old dna sample from the first 1974 crime scene. >> overnight we called 200 police men. we had helicopters, resources. we had a tank. >> we pull him over, and before he can hardly get it in park we're yanking him out of the

car. we put him down, and he looked at the detector who handcuffed him and said will you let my wife know i won't be home for lunch? i assume you know where i live. we got chills >> this man is the btk strangler. >> reporter: and you were still at that point convinced they had the wrong man? >> i think reality was starting to creep in, and i felt my stomach just twist, realizing it would be true. >> reporter: his confession recorded during police interrogation. >> it took a while for denis rader to start talk being, but once he did, he told police more than they bargained for. >> the belt that i used. >> he spoke for over 30 hours.

and he showed no remorse, no regret. the only regret he showed during this was that there weren't more victims. he told us that we would discover what he termed his mother lode. >> there were journals and drawings. he had material that he collected from each of his victims. clothing. car keys. >> he had compartments everywhere, false bottoms in the closet. stuff in the crawlspace, stuff in the treehouse he had made for his kids. >> reporter: one minute had a man in your life who you thought was a loving father. >> right. >> reporter: the next minute he's a serial killer. >> right. i had to learn to grieve the loss of somebody i loved very much that no one else loved anymore. >> reporter: up next, how kerry unwittingly played a part in her father's capture. >> it felt like an invasion of my privacy. >> reporter: plus, how she found it in her heart to forgive her

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"nightline" continues. here again, deborah roberts. >> btk is arrested. >> police say this man, 59-year-old denis rader is the btk strangler. >> reporter: after 30 years, the btk killer was finally in custody. >> we have learned that rader has been charged with ten counts now of first degree murder. >> reporter: the community in shock. denis rader was a serial killer

in plain sight. >> denis rader is literally the least-likely suspect. he is a pillar of the community. he's the president of his lutheran church congregation, a compliance officer. he wore a badge. >> reporter: it was his daughter kerry who unwittingly provided the information for the arrest. you had no idea. >> i had no idea. they found out i had annual pap smears. they got a sample of my dna. >> reporter: in some ways, your dna sealed your dad's fate. >> yes, it did, but nobody told me this. it would have been nice if someone had asked me for my dna, i would have willingly given it. it felt like an invasion of my privacy. >> he didn't think they had kept the biological samples from the crimes that he had committed all these years. and they brought up the dna, and they could nail him.

>> it's there. >> reporter: while he was in custody, the story of the btk killer became an international sensation. >> everybody wanted to talk to denis. i wrote him a number of letters and included my phone number. on one saturday morning i get a call. and the operator says, will you accept a collect call from the detention facility. i had btk on the phone. i have a recorder going, if that's all right with you. >> okay. c >> can you pinpoint when you knew there was a problem coming? >> i would say probably grade school. >> and what kind of problems were those? >> oh, sexual things. >> he talked about the hunt.

he told me he got a high from it. finding the woman, and then killing her. that was what turned him on. >> do you have any remorse over the killings? >> remorse? >> yeah. >> yes, i do. >> denis rader told me he felt sorry for the victims, although no one believes that. >> it was more like he was sorry he got captured. >> after i hung up the phone, i remember thinking, i just talked to a man who has no soul. >> reporter: fac ovehelming eviden of his ra plded guilty. >> the plea hearings are usually ten, 12 minutes, but this one turned into about an hour and a half. >> reporter: with the courtroom transfixed in horror, later,

recalling the agonizing details of every murder. >> i had never strangled anyone before, so i really didn't know how much pressure to put on a person or how long it would take. i tied her up and put a bag over her head and strangled her >> here is this man standing up in court in what i imagine was his church suit, recounting the murders of his neighbors, one by one by one. >> he makes himself sound like he's mr. good guy, you know, like he says, i got mr. yoe t pillow before i strangled him. >> he had a cracked rib from an accident, so i had him put a pillow down for his head. >> >> reporter: i was kind to him before i killed him. >> that's where that massive disconnect comes in, and you realize, my god, my father's a psychopath. >> reporter: later at the

sentencing, he was confronted by the victims' family members. >> i have wondered what it would be like to confront the walking cesspool that took my mother's life. >> reporter: then he was allowed to address the court. >> thanks. i can't believe the people. they've done a lot of work. i hope i pronounce these people's last names right. >> all the families walked out. they all got up, turned around and walked out the door. >> he's thanking everybody like the police, and then he basically said like my family were pawns in his game and social contacts. >> reporter: the judge condemning rader to ten life sentences, the harshest punishment at that time. do you think your mom had any clue he was doing anything criminal? >> no, mom and i both said if we had had an inkling that my father had harmed anyone, let alone murdered anyone, let alone

ten, we would have gone screaming out that door to the police station. we looked like a normal american family, because we were a normal family. >> reporter: your book is called "a serial killer's daughter." is that how you see yourself? >> it's taken me a long time to even be able to say that out loud, but that's the truth. >> reporter: kerry has now been able to forgive her father and is in touch with him. >> >> you will always be my baby girl. hopefully your heart will mend. the dark side took me away. >> reporter: how could you even correspond with him? i mean, people would wonder, why wouldn't you just cut him off? >> i wasn't corresponding with btk. i'm never corresponding with btk. i'm talking to my father. i'm talking to the man that i lived with and loved for 26 years. i still love my dad today.

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after the story first aired on abc, kerry gave us a statement, saying she had received a letter from her father in february, in which he said he'd watched a lot of interviews she'd done for her book. she says she is not currently in contact with him and that she has been in an extended period trying to recover in that she was in an ongoing period of trying to rest and get peace and space. she added our family has moved, embracing a new start for all of us. that's "nightline." you can always catch our full episodes on hulu. thanks for the company, america. have a good weekend.