this is a special edition of "nightline." a mother's reckoning. >> tonight, the massacre at columbine high school. a tragedy that shocked a community and left the nation asking what drove two teenagers to take the lives of 13? what kind of people were their parents? >> could you have prevented what happened at columbine? >> after 17 years, sue klebold, mother of one of the shooters, break her silence. much. them? >> one mother's quest, looking for the path of her son's descent and the clues she says she missed. >> the one thing of course that i want to say is, i am so sorry for what my son did. >> tonight, an important conversation about the warning signs that may prevent tragedy. >> this special edition of

reckoning, will be right back. there are those who say we cannot defeat a corrupt political system and fix a rigged economy. but i believe we need to lift our vision above the obstacles in place and look to the american horizon. to a nation where every child can not only dream of going to college, but attend one. where quality healthcare will be a birthright of every citizen. where a good job is not a wish, but a reality. where women receive equal pay and a living wage is paid to all. an america where after a lifetime of labor, there is time for rest and grandchildren.

but no longer carries so much of that burden alone. i know we can create that america if we listen to our conscience and our hearts and not to the pundits and the naysayers. i'm bernie sanders. i approve this message, and i ask for you to caucus for me. thank you. 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 boy and all she believed he 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

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. and for the years to come, we would all be asking the same questions -- who were these killers? and what kind of parents could produce children like these?

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? . the one thing, of course, that i want to say is, i am so sorry for what my son did. yet i know that just saying i'm

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. golden hair. it was just thick and round 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. before columbine left-hand side,

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. that god stopped this. just make it stop. don't let him hurt anybody. >> reporter: but by the end of

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 five or six of them at the same 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. >> reporter: she says she does 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

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 i want to be accepted. 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

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. >> reporter: around the same time, a series of troubling events. he hacks into the school computer system with some friends. they're all suspended for three days.

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. >> it was terrible, i know, 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 lectures, trying to reason with him. >> i even talked about the ten commandment commandments, it's wrong to steal, in no circumstances this is right. and then we responded as most parents would. we took away privileges. >> reporter: one night she's frustrated, he's not doing chores, he's withdrawn, she pushes him against the refrigerator. >> i said, you've got to stop thinking of yourself, you've got to stop being so selfish. but -- excuse me. but i gave him the old mom

and then i said, by the way, today's mothers day and you forgot it. and i don't remember how that confrontation ended. i just remember he softly said, mom, please don't push me, i don't know how much i can control myself. it wasn't a scary thing. it was just him being nice to say, back off, please. >> reporter: she says she a little -- it was a little . and i thought everything was fine. because he was so -- he was so sweet. when we come back, the secret journals. what do they reveal about the minds of two teenagers responsible for columbine? and what forced sue klebold to finally face the truth about her son?

might prevent a tragedy. the setting is just right. there's something in the air. but here's the thing: about half of men over 40 have some degree of erectile dysfunction. well, viagra helps guys with ed get and keep an erection. ask your doctor if your heart is healthy enough for sex. do not take viagra if you take nitrates for chest pain or adempas for pulmonary hypertension your blood pressure could drop to an unsafe level. to avoid long-term injury, seek immediate medical help for an erection lasting more than four hours. stop taking viagra and call your doctor right away if you experience a sudden decrease or loss in vision or hearing. ask your doctor... ...about viagra. available in single packs. covergirl makes flawless as easy as... one... "tru"... three. with new trublend primer preps and smooths skin and trublend makeup blends flawlessly plus new trublend blush and bronzer

it's just a cough. if you could see your cough, you'd see just how far it can spread. robitussin dm max soothes your throat and delivers fast, powerful cough relief. robitussin dm max. because it's never just a cough. the bold nissan rogue, with intuitive all-wheel drive. because winter needs a hero. now get a $189 per month lease on the 2016 nissan rogue. nissan.

flores: i was raised by my father. my mother left my family when i was 9 years old. things really went from bad to worse for me. this isn't just about numbers, this is about real lives. this is a system that isn't working for the everyday person. it's one of the reasons why i decided to endorse bernie sanders. nevadans are looking for people who are willing to think big, to be bold, and to fight for everyday people. and that's exactly what bernie sanders is doing. sanders: i'm bernie sanders

this special edition of "nightline" continues. >> look at a kind of class picture. can you pick out which ones will grow up to be school shooters? almost two-thirds will be from two-parent homes. nearly half of the kids will do well in school. 73% of them will never have been arrested before. and yet every child you see here 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

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 secret journal, and his journal is filled with venomous threats, graphic fantasies about revenge on people who have insulted him.

dated heads. according to o'toole it signals a personality disorder, a psychopathic brain. >> these are people without a 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. >> reporter: dylan stumbles. >> it's a good thing we uh -- we ordered those radio [ bleep ] -- >> reporter: the camera shuts down.

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. committing suicide or going nbk with eric. nbk, natural-born killers, the violent revenge movie by oliver stone.

question about dylan klebold. why did he go from suicidal to homicidal? did eric infect him with a k 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 athe pizzeria where dylan worked had seen the two boys experimenting with a pipe bomb. and perhaps most shocking of all the police knew eric had a website. ten pages of savage threats. some frightened parents had alerted them. police started to draw up a search warrant.

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 recorded as a kind of countdown to the attack. >> it was horrible to see those tapes. they were posturing. they were acting tough. they were talking about all the horrible things they were planning to do. >> reporter: but as we said, she lives in the hell of that contradiction. she has said, i saw the end product of my life's work. i had created a monster. but still, inside her, a mother's love for a son she lost.

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 students who overheard something, tipped off authorities. >> most of the time it is nothing.

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. like, of course. that perhaps i'm intruding. >> reporter: but someday if you go to that memorial, you just

sitting there quietly alone. >> sometimes i just sit there. and think. and i tell them i'm sorry. >> 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, to get 0% financing for 60 months on a ford suv.

ford explorer...edge...escape... and expedition... the world a president has to grapple with. sometimes you can't even imagine. that's the job. and she's the one who's proven she can get it done. ...securing a massive reduction in nuclear weapons... ...standing up against the abuse of women... ...protecting social security... ...expanding benefits for the national guard... ...and winning health care for 8 million children... the presidency is the toughest job in the world and she's the one who'll make a real difference for you.

there are 16 million children struggling with hunger in america. that's 1 in 5 daughters, sons, neighbors, and classmates who don't know where their next meal is coming from. yet billions of pounds of good food go to waste every year. it's time we do something about it. feeding america is a nationwide network of food banks that helps provide meals to millions of kids and families in need. visit feedingamerica.org to help them feed even more. together we can solve hunger.

to learn more about all the issues raised tonight and for resources about mental health and suicide prevention, you can head to our website at abcnews.com. thank you for watching. tune into "good morning america" tomorrow. and as always, we're online 24/7 on now on "ok! tv." new video lamar odom's first public appearance since his near fatal overdose. kim k. goes blonde, caitlyn back stage. we've got the sold out madison square garden spectacular. >> justin bieber all grown up on his gq cover. the pop star dish's life, love and who he says keeps him out of trouble. then how ageless beauty naomi campbell looks this fierce at 45.

at the movies for grownups awards. >> we're raising a lot of money tonight. >> we crash his beverly hills date night with catherine zeta-jones. >> plus -- >> you know i try but don't do too well with apologies. >> plus what has them apologizing? >> is it too late to say i'm sorry? >> big stars, big movies, big tv shows. your entertainment news source starts now. welcome to "ok! tv." i'm in the heart of new york city with all of your entertainment news. let's get things started with the hollywood wrap. a thousand models, the jenners, the kardashians and a sold-out madison square garden. this is how kanye west unleashes a mega new york fashion event debuting his season three line pablo."