The mother of one of the Columbine High School shooters says in her first television news interview that she never suspected her son was capable of the violence he committed on April 20, 1999.

Sue Klebold said she believed she had an open, communicative relationship with her son Dylan. She now marvels at the disconnect between her perception and reality.

“I felt that I was a good mom, that he would, he could talk to me about anything,” Klebold told ABC News’ Diane Sawyer. The interview was to air Friday night on “20/20.”

“Part of the shock of this was learning that what I believed and how I lived and how I parented was an invention in my own mind,” she said. “That it was a completely different world that he was living in.”

Dylan Klebold and his friend Eric Harris gunned down 13 people and injured 24 others before killing themselves in a massacre that shook the nation.

Early reports said the boys were victims of bullying, but later research showed another possible motive: They intended to commit an act so atrocious it would dwarf the carnage of the Oklahoma City bombing, in which 168 people were slain. The explosives they brought to school failed to detonate but could have killed hundreds.

advertisement | advertise on newsday

“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,” Sue Klebold said. “And, it’s very hard to live with that.”

Sawyer said Klebold wants to help parents identify signs of violence in their own children.

The interview coincides with the release of Klebold’s memoir, “A Mother’s Reckoning: Living in the Aftermath of Tragedy.” Profits will go toward research and charitable groups focused on mental health.