Washington - Sue Klebold, the mother of a teen involved in the deadliest high school shooting in US history, said she saw no signs of her son's mental distress in her first TV interview since the 1999 massacre.
Klebold's son Dylan, 17, and his best friend Eric Harris, 18, came to school on April 20, 1999 dressed in black trenchcoats and carrying four guns. They opened fire, killing 13 people and wounding 24 in Columbine before killing themselves.
Nearly 17 years have passed since that fateful day, and Klebold said in an interview with ABC's 20/20 news show that has been living with guilt ever since.
"I am so sorry for what my son did," Klebold, 66, said.
"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."
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Klebold said 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 last moments of his life were spent in violence, sadism. You know, he was cruel and hateful and and I have to own that."
If a kid had shot her son, she said she immediatly would have blamed the child's parents.
"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 I wasn't able to stop his hurting other people. I wasn't able to stop his hurting himself. And it's very hard to live with that."
There were no signs of Dylan's murderous tendencies, Klebold said.
"If I had recognized that Dylan was experiencing some real mental distress, he would not have been there. He would've gotten help.
"I don't ever, for a moment, mean to imply that I'm not conscious of the fact that he was a killer, because I am," she said.
Klebold, who also spoke to other media outlets including the BBC, has described her ordeal in her book titled "A Mother's Reckoning." She said that all profits from the book sales will go to mental health charities.