The mother of one of the survivors of the 1999 Columbine High School massacre says she's glad the mother of shooter Dylan Klebold has finally opened up about her feelings about what her son did.

Connie Michalik, whose son Richard Castaldo was shot in the chest and back and was left paralyzed from the waist down, says after 10 years, she never thought she'd hear from Susan Klebold. But she's impressed that Klebold has broken her silence by publishing an essay in O, The Oprah Magazine.

In the essay, entitled "I Will Never Know Why," Klebold writes that she had "no inkling" Dylan was depressed, suicidal and filled with rage at his peers.

"For the rest of my life, I will be haunted by the horror and anguish Dylan caused. I cannot look at a child in a grocery store or on the street without thinking about how my son's schoolmates spent the last moments of their lives," Klebold writes. "Dylan changed everything I believed about myself, about God, about family, and about love."

Michalik says she was glad to see the article because all these years, she's wondered whether Klebold was suffering the way she was.

"I was glad to finally hear from her. I needed to know how she felt. I knew what I was going through, which was hell. I needed to know what she was going through," Michalik told Canada AM Wednesday.

Klebold writes that there was so much she didn't know about her son before he and pal Eric Harris killed 12 students, a teacher, wounded 23 others, and then killed themselves. She didn't know her son was collecting guns and was so depressed, that he was bent on murder, Klebold says. And she had a hard time accepting it.

"We believed his participation in the massacre was accidental or that he had been coerced. We believed that he did not intend to hurt anyone,"she writes.

Michalik says she believes Klebold when she says she had no idea what her son was planning.

"I honestly don't believe she knew. I know several families whose children have committed suicide and they had no idea either. I do believe her when she says she didn't have an inkling," she said.

Michalik points out that it's often hard for parents of teenagers to know what's going on in their kids'  lives outside of home.

"I'm a teacher and I know teachers are with teenage kids usually more than the parents are. The kids come home from school and they eat dinner and then go off to extracurricular activities, then they go to bed. You don't see your teenage children that much. But teachers see them more," she said.

For that reason, she places a lot of the blame for the tragedy at the feet of the school's staff.

She says Dylan Klebold wrote essays and videos filled with violent images -- essays that school staff read. And yet, no one alerted his parents that Klebold was clearly depressed.

"There were too many people who knew at the school and they never got together and had a meeting. No one said anything. If they had just compared notes, I think they would have had a clue something was going on," Michalik said.

Klebold's mother writes that when she read the essays later, they broke her heart, because they revealed an inner turmoil she had no idea her son was going through.

"Dylan's participation in the massacre was impossible for me to accept until I began to connect it to his own death. Once I saw his journals, it was clear to me that Dylan entered the school with the intention of dying there. And so in order to understand what he might have been thinking, I started to learn all I could about suicide," she writes.

Michalik says her son Richard is now a sound engineer, working for the Showtime network in Los Angeles. He moved there three years ago, after growing tired of being "the Columbine kid" in his hometown.

She says she learned later that Dylan Klebold was also learning how to be a sound technician. She says her son later realized they had things in common and that maybe they could have been friends.

"That's what Richard told me, he said: 'I wish we had been friends; maybe I could have prevented this.' Richard has a very big heart and he's very forgiving. The whole thing was such a tragedy," she says.

Her son still struggles at times, Michalik says, and she too remains broken-hearted. But she's glad to have heard from Susan Klebold and applauds her bravery, knowing that it will never take away her pain.

"You get through it," Micahlik says, "but you never get over it."