thi of "nightline." a mother's reckoning. >> tonight, the massacre at columbine high school. y that shocked a community and left the nation asking what drove two teenagers to take the lives of 13? parents? >> could you have prevented what happened at columbine?

this is a special edition of "nightline," a mother's reckoning. >> good evening and thank you for join us. tonight the powerful and untold story of the mother of one of the columbine shooters. nearly two decades later, sue klebold is speaking out. the mother trapped in contradiction between a little

could be and the murderer he became. and especially for the families of the victims, those urgent and anguished questions never answered, until now. constitute massacre have been prevented, and warning signs that may have been missed. here's abc's diane sawyer. >> reporter: it is 1999. a shock wave hits america. two high school boys in trench coats carrying shotguns, a semiautomatic weapon, and homemade bombs walk into their school and begin the slaughter of their classmates. who were sitting on the grass eating their lunch. who were hiding under tables. no defense from the terror. 13 are kill the. 24 are wounded. and we are all watching for the first time children run out of their school fleeing mayhem. >> a lot of students -- >> coverage of the columbine -- >> reporter: we see a wounded student struggling out the window of his high school to escape with his life.

would all be asking the same questions -- who were these killers? and what kind of parents could produce children like these? >> someone wasn't doing their job. >> reporter: for 17 years now, the parents of dylan klebold and eric harris have lived their secrets, unwilling to step forward. until a gray-haired woman makes her way into a room. in the course of this day at one point we see her pacing. perhaps grappling with her decision to step forward after 17 years hiding from cameras. years of being hated, threatened, she says afraid and ashame the. so klebold is now 66 years old. for the families of 13 people who died and 24 people who were injured, most of them children, what is it you want to say to them? .

want to say is, i am so sorry for what my son did. yet i know that just saying i'm sorry is such an inadequate response to all this suffering. there is never a day that goes by where i don't think of the people that dylan harmed. >> you use the word harmed. >> i think it's easier for me to say harmed than killed. it's still hard for me after all this time. >> is that about a certain need to deny what happened? >> i don't know. perhaps. perhaps. >> reporter: she seems to be trapped in a contradiction. remembering the son she once had and the murderer he became. >> called him the sunshine boy? >> we did when he was little, yeah. he had this sort of a mane of golden hair.

and -- he was such a happy, precocious, brilliant little child. >> for all the parent hot have said, i would have something, i would have just known. >> i know. before columbine left-hand side, i would have been one of those parents. and i guess that's why certainly why i'm here talking to you today. >> reporter: she has written a book called "a mother's reckoning." in it she says all the lessons of her regret which began on the day she woke up an ordinary wife and mother, fast forward 24 hours and i was the mother of a hate-crazed gunman. she remembers the shocking prayer she found herself praying after learning her son might be one of the columbine shooters and the shooting was still going on. >> the police were there. the helicopters were going over. and i remember thinking, if this is true, if dylan is really hurting people, he has -- somehow he has to be stopped. and then at that moment i prayed that he would die.

just make it stop. don't let him hurt anybody. >> reporter: but by the end of the day, her son and his friend would take the lives of 13 people and then take their own. in her book sue klebold writes, her son wasn't the pinwheel-eyed portrait of evil we know from cartoons. he was shy, like bible, hands-on parents, put them to bed with stories and prayers and hugs. >> reporter: sue klebold calls dylan her shiny penny. in gifted classes. loved little league. gave big hugs and kisses. built tall ships out of legos. >> he wouldn't just work on one puzzle, he'd dump them into a big mountain so he could solve time. >> reporter: she says he was easily embarrassed, tearful and hard on himself if he made a mistake. shy heading into adolescence. >> he talked about looking weird? >> he was a tall, gawky kid with glasses.

notice something, that dylan seems to be losing interest in good grades. but she now says, as she looks back over her life, she is male a big mistake. her son is changing. but she writes off the changes. as an adolescent phase. >> sometimes he would seem distant or quiet. and i remember asking him, are you okay? are you sure you're okay? you seem so tired. and he'd stand up and say, i've got a lot of homework, i need to go to bed. >> and you'd let it go. >> i let it go. and that's the difference. i would dig. if it were me today, i would dig and dig and dig. >> reporter: she has no idea her 15-year-old son has begun a secret journal. and his first entry is this. thinking of suicide. i hate my life, i want to die. i have a nice family, good house, couple of good friends. no girls. nobody accepting me even though

but at this point we want to be very clear -- 80% to 90% of depression can be treated. and even suicidal depression is not an explanation for a pathway to violence. dr. gregory fritz wants to warn parents tonight that suicidal depression is real and can strike any teen anywhere. >> somewhere between 15% and 20% of high school kids say that they have thought about suicide in the past year. >> reporter: but more than 17 years ago, sue klebold says she knew so little about teen depression. >> could you have prevented what happened at columbine? >> if i had recognized that dylan was experiencing some real mental distress, he would not have been there. he would have gotten help. >> reporter: in this video from his junior year he seems self-conscious but talks about the future, going to college. >> so you get better chances at high school as far as college goes, maybe a scholarship.

time, a series of troubling events. he hacks into the school computer system with some friends. days. he scratches an epithet on the locker of a kid he thinks is taunting him. then the big shock, he and another kid break into a van, steal electronic equipment, and police make an arrest. >> this is a felony, two felony counts. absolutely. it was awful. and at the time i thought that was the worst thing i could ever possibly experience. >> reporter: dylan's cold reaction after the arrest scared and shocked her. he acted as if he had done nothing wrong. she says she gave him one of her

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will become a school shooter. in total murdering 67 people. the child in this picture is dylan klebold. >> i don't think he was always a violent young man. i think it evolved over time. i think it took a lot of time. >> reporter: we brought in former fbi agent mary ellen o'toole, one of the world's leading profilers of the criminal brain. she has analyzed thousands of pages of evidence on columbine and dylan klebold. >> you don't think school shooters just snap one day? >> absolutely not. i have not ever seen where that has happened. i think he was in a very destructive friendship which was very powerful. maybe even more powerful than what we think. >> reporter: there is no way to continue telling this story without going back to another little face in that class picture. a friend who was with him breaking into the van. eric harris. he would become the other shooter at columbine that day. he has also begun to keep a

is filled with venomous threats, graphic fantasies about revenge on people who have insulted him. people engulfed in flames, detap dated heads. according to o'toole it signals psychopathic brain. conscience. these are became without empathy, without guilt. >> reporter: is eric harris really different from dylan klebold? another expert on columbine, dr. peter lang man, insists he is. >> eric liked to draw weapons, swastikas, wrote about the nazis. dylan drew hearts. dylan wrote about his search for true love. eric when he does refer to girls, his fantasy is raping them. >> reporter: in their senior year, eight months before columbine, the two boys spent more time together. they liked violent movies and making little movies of their own. trying on what it's like to be tough guys. eric is smooth. >> i think we might have to get some more weaponry.

>> it's a good thing we uh -- we ordered those radio [ bleep ] -- >> reporter: the camera shuts down. eric writes, everyone is always making fun of me because of how i look, how weak i am. guns, i need guns. dylans and for one too. >> and i had told him no. >> reporter: sue klebold said she used to look through his room during his junior year, but by his senior year she decided to respect his privacy with distance and regret she now says how wrong that decision was. >> would you ransack his room now? >> i would. i'd do it as if his very life was depending on it. and i would do it with love. >> reporter: the boys were already getting their hands on guns and hiding them. a girl, a school friend old enough to buy them legally, got them three at a gun show. she trained at a range. and dylan klebold writes, he now has a choice.

with eric. nbk, natural-born killers, the violent revenge movie by oliver stone. which brings us to the central question about dylan klebold. why did he go from suicidal to homicidal? did eric infect him with a kind of pathological virus? or was it dylan's presence that reinforced eric's violent fantasies? >> do you think dylan klebold knew right from wrong? >> yes, absolutely he did. but it did not preclude him from being able to participate in the planning and to carry it out. >> do you believe in evil? >> i don't think so. i don't think i do. >> reporter: but o'toole says there were signs that were missed and that it's striking how many other people might have raised an alarm. it turns out the boss at the pizzeria where dylan worked had seen the two boys experimenting with a pipe bomb. and perhaps most shocking of all

ten pages of savage threats. some frightened parents had alerted them. police started to draw up a search warrant. but thinking they don't have enough do nothing. sue klebold says for months and months her mind was looking for any way to deny the truth. >> i believed this was a moment of madness. i believed this was some impulsive fluke that happened suddenly. >> reporter: it wasn't until six months after columbine her denial is shattered. the lead investigator in the case who brings them face-to-face with the inescapable truth of the evidence. dylan took part in months of planning. and there he was on videotape to the attack. tapes. they were posturing. they were acting tough. horrible things they were planning to do. >> reporter: but as we said, she lives in the hell of that contradiction.

product of my life's work. i had created a monster. but still, inside her, a mother's love for a son she lost. she hears the final word on the tape. he says, "hey, mom, i got to go." >> just want to apologize for any crap this may bring. just know i'm going to a better place. good-bye. >> he said mom. just the fact that he said it meant a lot to me. yeah. >> reporter: the tapes never released. we're told they've now been destroyed. since columbine, law enforcement says there have been 50 rampage school shootings. abc news has estimated at least 79 thwarted plots. more than half of them mentioning columbine. so what can we do about the shooting at schools? prevention can work but how? in dozens of cases it is fellow

something, tipped off authorities. >> most of the time it is nothing. but maybe it's just that one peek into what could be the next columbine. >> reporter: last week we tried to call every single family. some of them expressed anger. others said they preferred to move on. some said they wanted to offer sue klebold their prayers and grace. so many people, as someone said, sentenced to a life of grief with no parole. after our interview is over, she walks outside in the foothills of the rocky mountains and tells us sometimes she finds herself drawn to a place that has a plaque with these words. it brought a nation to its knees. what have we learned? it's the columbine memorial. >> i feel a kind of unwelcome there.

that perhaps i'm intruding. >> reporter: but someday if you go to that memorial, you just might see a gray-haired woman sitting there quietly alone. >> sometimes i just sit there. and think. >> reporter: for "nightline," i'm diane sawyer. >> our thanks to diane sawyer. sue klebold has written a memoir called "a mother's reckoning: living in the aftermath of tragedy." all the book's profitsless toward research and charitable foundations focusing on mental health issues. we'll be right back. shopping for an suv? well, this is the time. and your ford dealer is the place,

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