LITTLETON, Colorado – The destruction and devastation of a mass shooting lingers long after the immediate incident, tearing apart families, friendships and communities as survivors struggle with guilt, loss and post-traumatic stress.

Columbine school shooting survivor Zach Cartaya, 37, knows that all too well.

He lost 12 classmates and a coach on that April day nearly 20 years ago, and suicide deaths have claimed more of his friends over the intervening years. 

"These things ripple out. A stone drops in a pond and it all ripples out. And I understand that better now than when I was younger," Cartaya said. "We've lost so many people along the way: that isolation, that grief, that anger manifests in the worst possible ways. It's awful, it's devastating, but unfortunately it's not shocking."