(CNN) Her son and his friend killed 13 people at Columbine High School almost 17 years ago. Sue Klebold has lived with guilt since -- guilt for what her son did and how she, a loving mother, raised a boy who became a mass murderer.

She has spoken only a few times to the media in the past, but has never appeared on television. Her first TV interview, given to ABC's Diane Sawyer, aired Friday night.

In it she talks about what life has been like after April 20, 1999, when her son, Dylan Klebold, and schoolmate Eric Harris committed what is the deadliest high school shooting in U.S. history. Clad in black trenchcoats and wielding four guns, the pair worked their way through the Colorado school after their plan to blow up hundreds of classmates failed.

Howard Unruh, a World War II veteran, shot and killed 13 of his neighbors in Camden, New Jersey, in 1949. Unruh barricaded himself in his house after the shooting. Police overpowered him the next day. He was ruled criminally insane and committed to a state mental institution.

Howard Unruh, a World War II veteran, shot and killed 13 of his neighbors in Camden, New Jersey, in 1949. Unruh barricaded himself in his house after the shooting. Police overpowered him the next day. He was ruled criminally insane and committed to a state mental institution.

Officers in Austin, Texas, carry victims across the University of Texas campus after Charles Joseph Whitman opened fire from the school's tower, killing 16 people and wounding 30 in 1966. Police officers shot and killed Whitman, who had killed his mother and wife earlier in the day.

Officers in Austin, Texas, carry victims across the University of Texas campus after Charles Joseph Whitman opened fire from the school's tower, killing 16 people and wounding 30 in 1966. Police officers shot and killed Whitman, who had killed his mother and wife earlier in the day.

Prison guard George Banks is led through the Luzerne County courthouse in 1985. Banks killed 13 people, including five of his children, in Wilkes-Barre, Pennsylvania, in September 1982. He was sentenced to death in 1993 and received a stay of execution in 2004. His death sentence was overturned in 2010.

Prison guard George Banks is led through the Luzerne County courthouse in 1985. Banks killed 13 people, including five of his children, in Wilkes-Barre, Pennsylvania, in September 1982. He was sentenced to death in 1993 and received a stay of execution in 2004. His death sentence was overturned in 2010.

In October 1991, George Hennard crashed his pickup through the plate-glass window of Luby's Cafeteria in Killeen, Texas, before shooting 23 people and committing suicide.

Eric Harris, left, and Dylan Klebold brought guns and bombs to Columbine High School in Littleton, Colorado, in April 1999. The students gunned down 13 and wounded 23 before killing themselves.

Pallbearers carry a casket of one of Michael McLendon's 10 victims. McLendon shot and killed his mother in her Kingston, Alabama, home, before shooting his aunt, uncle, grandparents and five more people. He shot and killed himself in Samson, Alabama, in March 2009.

Jiverly Wong shot and killed 13 people at the American Civic Association in Binghamton, New York, before turning the gun on himself in April 2009, police said. Four other people were injured at the immigration center shooting. Wong had been taking English classes at the center.

A military jury convicted Army Maj. Nidal Hasan of 13 counts of premeditated murder for a November 2009 shooting rampage at Fort Hood, Texas. Thirteen people died and 32 were injured.

Connecticut State Police evacuate Sandy Hook Elementary School in Newtown, Connecticut, in December 2012. Adam Lanza opened fire in the school, killing 20 children and six adults before killing himself. Police said he also shot and killed his mother in her Newtown home.

Police officers walk on a rooftop at the Washington Navy Yard after a shooting rampage in the nation's capital in September 2013. At least 12 people and suspect Aaron Alexis were killed, according to authorities.

A man kneels across the street from the historic Emanuel African Methodist Episcopal Church in Charleston, South Carolina, following a shooting in June 2015. Police say the suspect, Dylann Roof, opened fire inside the church, killing nine people. According to police, Roof confessed and told investigators he wanted to start a race war. He was eventually convicted of murder and hate crimes, and a jury recommended the death penalty.

Police search students outside Umpqua Community College after a deadly shooting at the school in Roseburg, Oregon, in October 2015. Nine people were killed and at least nine were injured, police said. The gunman, Chris Harper-Mercer, committed suicide after exchanging gunfire with officers, a sheriff said.

In December 2015, two shooters killed 14 people and injured 21 at the Inland Regional Center in San Bernardino, California, where employees with the county health department were attending a holiday event. The shooters, Syed Rizwan Farook and his wife Tashfeen Malik, were later killed in a shootout with authorities. The pair were found to be radicalized extremists who planned the shootings as a terror attack, investigators said.

Police direct family members away from the scene of a shooting at the Pulse nightclub in Orlando in June 2016. Omar Mateen, 29, opened fire inside the club, killing at least 49 people and injuring more than 50. Police fatally shot Mateen during an operation to free hostages that officials say he was holding at the club.

A couple huddles after shots rang out at a country music festival on the Las Vegas Strip on Sunday, October 1, 2017. At least 58 people were killed and almost 500 were injured when a gunman opened fire on the crowd. Police said the gunman, 64-year-old Stephen Paddock, fired from the Mandalay Bay hotel, several hundred feet southwest of the concert grounds. He was found dead in his hotel room, and authorities believe he killed himself and that he acted alone. It is the deadliest mass shooting in modern US history.

Investigators at the scene of a mass shooting at the First Baptist Church in Sutherland Springs, Texas, on Sunday, November 5, 2017. A man opened fire inside the small community church, killing at least 25 people and an unborn child. The gunman, 26-year-old Devin Patrick Kelley, was found dead in his vehicle. He was shot in the leg and torso by an armed citizen, and he had a self-inflicted gunshot to the head, authorities said.

Parents wait for news after a shooting at Marjory Stoneman Douglas High School in Parkland, Florida, on Wednesday, February 14. At least 17 people were killed at the school , Broward County Sheriff Scott Israel said. The suspect, 19-year-old former student Nikolas Cruz, is in custody, the sheriff said. The sheriff said he was expelled for unspecified disciplinary reasons.

Images of terrified students being led from the school with their hands on their heads became ingrained in national memory.

Missed warning signs

Sue Klebold never thought her son would do anything so horrific.

"I had all those illusions that everything was OK because, and more than anything else, because my love for him was so strong," she says in the interview, according to a snippet released Thursday.

JUST WATCHED 2012: Lessons of recovery from Columbine Replay More Videos ... MUST WATCH 2012: Lessons of recovery from Columbine 02:35

When her discussion with Sawyer turns to how many other parents insist they would have seen warning signs and been able to prevent the shootings, she says, "Before Columbine happened I would have been one of those parents."

"If I had recognized that Dylan was experiencing some real mental distress, he would not have been there," she says. " He would've gotten help. I don't ever, for a moment, mean to imply that I'm not conscious of the fact that he was a killer, because I am."

In a 2009 essay for O magazine , Klebold wrote that her son had a fun childhood but when he became a teenager things changed. She just didn't think the worst, though. She wrote in O that she thought her maternal instincts would keep him safe. She would know if there was trouble.

She tells Sawyer that one of the things that has haunted her has been the thoughts she has almost every day about the children and the teacher who needlessly died.

"I just remember sitting there and reading about them," she says while holding back tears, "... all these kids and the teacher. ... and I keep thinking, (have) 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 has said previously that she and her husband don't understand why their son took part in the massacre.

One of the survivors of the massacre wrote a Facebook post directed to the mother.

Anne Marie Hochhalter was paralyzed after being shot.

She said she has no ill will toward Sue Klebold and wouldn't judge her for the actions of others.

"I have forgiven you and only wish you the best," Hochhalter wrote

Hochhalter said that she was touched by a lengthy letter she received from the Klebolds a few months after the shooting.

A cautionary tale for parents

Klebold hopes her story, which she tells in a book to be released next week , will help other parents spot potential signs of trouble with their children.

Dylan Klebold was 17 when he and Harris,18, carried out their long-planned attack on the high school about 13 miles south of downtown Denver. After 49 minutes in which they killed 13 and injured 24 others, they each committed suicide.

The death toll could have been much, much worse; homemade propane bombs left in a cafeteria where hundreds of students were eating lunch failed to go off. Neither did bombs planted in their cars that were designed to kill people who responded to the scene.

JUST WATCHED 2012: Columbine survivor on school shootings Replay More Videos ... MUST WATCH 2012: Columbine survivor on school shootings 01:30

"I wish I had known then what I know now: that it was possible for everything to seem fine with him when it was not, and that behaviors I mistook as normal for a moody teenager were actually subtle signs of psychological deterioration," Sue Klebold wrote on the website for her book.

In his junior year, Dylan hacked the school computer system, she said. He scratched some hateful words on a kid's locker and he and others broke into a van and got arrested.

"He acted cold, like he had done nothing wrong." She and the father lectured him, took away privileges. Meanwhile, he was writing in his journal that he wanted to get a gun. She confronted him one night and gave him "the old mom lecture. And I said, 'By the way it's Mother's Day and you forgot it. ... He said, 'Mom don't push me.' "

He went out and bought a little gift and she thought everything was fine.

In the O essay, she talked about raising Dylan.

" I taught him how to protect himself from a host of dangers: lightning, snake bites, head injuries, skin cancer, smoking, drinking, sexually transmitted diseases, drug addiction, reckless driving, even carbon monoxide poisoning. It never occurred to me that the gravest danger -- to him and, as it turned out, to so many others -- might come from within. Most of us do not see suicidal thinking as the health threat that it is. We are not trained to identify it in others, to help others appropriately, or to respond in a healthy way if we have these feelings ourselves."

Klebold will donate the profits from her book to charities devoted to mental health issues, her publisher said.