Seventeen years after 13 lives were taken at Columbine High School, the mother of one of the gunmen is speaking on television for the first time.
Sue Klebold, the mother of Dylan Klebold, talked to ABC's Diane Sawyer about the tragedy, the victims, the relationship with her son and what it was like inside their home.
Sue and Tom Klebold have said previously that they had no idea their son and the second gunman, Eric Harris, were accumulating weapons or that their son had been journaling about suicide.
The ABC News primetime special "Silence Broken: A Mother's Reckoning" airs Friday night at 9 p.m. MT on a special edition of 20/20 on Denver7.
Susan Klebold has previously described her feelings in an essay for Oprah Winfrey's "O'' magazine and in interviews for Andrew Solomon's book "Far from the Tree."
"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."
Sawyer reports on teenage mental health, potential clues that could help a parent learn if their child is in crisis, and if it is possible to prevent the next school shooting.
Klebold has written a book, A Mother’s Reckoning: Living in the Aftermath of Tragedy, which will be released on Feb. 15, 2016. Klebold is donating all of her profits from the book to research and to charitable foundations with a focus on mental health issues.