we were disturbed by the shooting because it took place at a busy mall filled with holiday shoppers. but these events don't stay with us for long. the dead are buried and the new cycle moves on. perhaps we have become enured to the horror. april, 1999, 12 students and one teacher, shot and killed in columbine, colorado, 21 more survived with gunshot wounds among them, craig scott. >> the day of the shooting at columbine, it was the worst day of my life. this is worse than columbine. these are little kids that we are talking about. and so many parents' hearts are breaks out there. and i'm sure that many little kids don't understand what happened. >> reporter: columbine is synonymous with mass shootings. the pictures of students fleeing the school are images we personalized. what would we do if something