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LITTLETON, Co. — Saturday marks twenty years since one of the most shocking killing sprees in America – the massacre at Columbine High School. It was the deadliest high school shooting in U.S. history at the time and sparked national debates on gun control, bullying and violence.

“You’re different after you go through something like this. You’re not the same person.”

Amy Over is two decades into what she describes as a journey – a continuous emotional struggle after surviving the mass shooting during her senior year at Columbine High School.

“That was your last day of school, right?”

“That was my last day of school. I just wanted to forget that it ever happened.”

Twelve of her classmates were killed as well as her basketball coach Dave Sanders when two seniors opened fire inside the school. Over ran out of the front door amid a hail of gunfire.

“I didn’t start my therapy journey until after I had my daughter.”

“And what happened?”

“I dropped her off at pre-kindergarten and I had a panic attack. I had chronic panic attacks for about two years. Debilitating panic attacks.”

Intensive therapy has helped her tackle her trauma and survivor’s guilt. More recently, her work on the Rebels Project – an organization formed by Columbine survivors to help victims of other mass shootings.

“It just makes you feel like you’re not alone in this fight You’re not alone.”

Today, she lives with her husband and two children not far from Littleton.

“We still have open wounds, invisible wounds, that people can’t see. And we are still fighting our own demons and our own battles.”

Over said she’s slowly moving forward, in a healing process that may last a lifetime.