Killer's mother: I never stop thinking of Columbine victims
The mother of Columbine High School killer Dylan Klebold has said she had no idea anything was wrong with her son before the attack and thinks about the victims and their families every day.
In a special edition of ABC News' 20/20 current affairs programme - her first TV interview since the shooting - Sue Klebold told presenter Diane Sawyer that before the attack on April 20 1999 she considered herself a parent who would have known something was wrong.
"I think we like to believe that our love and our understanding is protective, and that 'if anything were wrong with my kids, I would know'. But I didn't know, and it's very hard to live with that," she said.
"I felt that I was a good mom ... That he would, he could talk to me about anything.
"Part of the shock of this was that learning that what I believed and how I lived and how I parented was an invention in my own mind. That it, it was a completely different world that he was living in."
Wearing black trenchcoats and carrying four guns, Dylan Klebold and Eric Harris opened fire at the school in Littleton, Colorado, a suburb of Denver, after their plan to blow up hundreds of classmates failed.
They murdered 12 pupils and a teacher during their rampage before killing themselves. Twenty-four people were injured in the attack.
Mrs Klebold said that after the massacre happened "I just remember sitting there and reading about them, all these kids and the teacher".
"And I keep thinking - constantly thought how I would feel if it were the other way around and one of their children had shot mine. I would feel exactly the way they did. I know I would. I know I would.
"There is never a day that goes by where I don't think of the people that Dylan harmed."
"You used the word 'harmed'," Ms Sawyer said. Mrs Klebold replied: "I think it's easier for me to say harmed than killed and it's still hard for me after all this time.
"It is very hard to live with the fact that someone you loved and raised has brutally killed people in such a horrific way."
The interview coincides with the release of Mrs Klebold's memoir, A Mother's Reckoning: Living In The Aftermath Of Tragedy, on sale on Monday.
She has said the Sandy Hook shootings in 2012 helped convince her to share her story, and would be donating any profits from the book to mental health charities and research.