In April 1999, Eric Harris and Dylan Klebold opened fire at Littleton, Colorado's Columbine High School, killing 12 students and one teacher and injuring 24 during a 45-minute rampage that left the country stunned.
Almost 17 years later, Klebold's mother, Sue Klebold, will hold her first television interview with ABC News anchor to discuss her journey in the aftermath of one of the country's.
The interview will coincide with the release of her new memoir, "A Mother's Reckoning: Living in the Aftermath of Tragedy." Sue Klebold's book proceeds will go toward research and to charitable foundations focusing on issues.
After the massacre, parents, mental health experts and law enforcement agencies clamored to figure out, as well as understand, why two teenagers would enter a school armed and shoot up their fellow classmates and teachers. It was later learned that Harris and Klebold had planned the attack, and journals and "basement tapes" also chronicled an intent to blow up the school.
Sue and Tom Klebold have said previously that they had no idea their son and Harris were accumulating weapons or that their son had been journaling about suicide.
Experts who studied the case said they believed Harris was a psychopath, in touch with reality, well-liked and charming, who had seduced Klebold.
Journals kept by Klebold, who was reportedly in a program for highly intellectual students and was his father's chess partner, revealed that he had grown increasingly shy in his teenage years. He was bullied and had turned inward to journals.
Six years ago, Susan Klebold wrote an essay for O magazine discussing that tragic day, as well has her journey to wrap her head around her son's actions and then move forward.
"For the rest of my life, I will be haunted by the horror and anguish Dylan caused," Sue Klebold wrote in the 2009 essay. "Dylan changed everything I believed about myself, about God, about family and about love."
"A Mother’s Reckoning" will be released on Feb. 16, 2016 by Crown.