The mother of one of the Columbine killers is giving her first TV interview since 1999 tonight on 20/20 - find out how to watch it live online.

Sue Klebold, the mother of Columbine shooter Dylan Klebold, is speaking with Diane Sawyer tonight on ABC's 20/20. Almost 15 years after the massacre that left 12 students and one teacher dead in Columbine, Colo., Sue admits in the interview that she still thinks about the victims.

"I just remember sitting there and reading about them, all these kids and the teacher," Klebold says. "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."

She continues, "There is never a day that goes by where I don't think of the people that Dylan harmed," adding, "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."

Dylan and Eric Harris also wounded 24 other people before committing suicide. Sue admits that it's hard to reconcile with the knowledge of what her son did.

"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," she says. "And-- it's very hard to live with that."

The full interview airs tonight on 20/20 at 10 p.m. ET/PT on ABC.

Watch Sue Klebold's Interview On 20/20 Live Online Or On Mobile Devices

If you can't watch the ABC telecast on a TV, the network is offering a live stream on the ABC website.

ABC also has its own app on iOS and Android, where you can watch live TV.

Keep Up With Sue Klebold's Interview On 20/20 Via Social Media

Want to live tweet the 20/20 interview? Use the hashtag #2020 on Twitter.