Twelve years ago, on the quiet spring morning of April 20, 1999, in the shadow of the Rocky Mountains, a vicious shooting attack was unleashed on students and faculty at Columbine High School in Littleton, Colorado.

Hitting the airwaves for all to see, it unnerved parents nationwide as two students, Eric Harris, 18, and Dylan Klebold, 17, went on a shooting rampage that would kill twelve students and one teacher, injure 21, and end with the suicides of the two killers.