It's been 17 years since the Columbine massacre, and on Friday night's 20/20, ABC will air the first TV interview with the mom of killer Dylan Klebold. In her sit-down with Diane Sawyer, Sue Klebold reveals her feelings about the 1999 Colorado school attack in which her son, 17, and his friend Eric Harris, 18, took the lives of 12 students and one teacher and wounded 24 others before killing themselves, ABC News reports. "There is never a day that goes by where I don't think of the people that Dylan harmed," she tells Sawyer, adding that she uses the word "harmed" because it's still difficult for her to say "killed" and that it's "very hard to live with the fact that someone you loved and raised has brutally killed people in such a horrific way."
Klebold tells Sawyer that she never saw the tragedy coming and that she thought her relationship with her son was solid. "I felt that I was a good mom … that he would, he could talk to me about anything," she says. "Part of the shock of this was learning that what I believed and … how I parented was an invention in my own mind. [It] was a completely different world [than] he was living in." Klebold has a memoir about her experiences coming out Monday; she'll donate the profits to research and foundations dedicated to mental health issues, per ABC. (Read Sue Klebold's heart-wrenching 2009 essay in O Magazine.)