A report released by Colorado's Attorney General Ken Salazar, shows there were at least 15 contacts between officials and the student gunman, dating back two years before the shooting in 1999.
Since the tragedy, local schools such as John Edwards High School in Port Edwards have developed Crisis Action Plans.
"We have a procedure that's basically a lockdown, it shows how to lock down your room, what to do with the students, where in the room should they be so they're not visible from the hallway," says Principal Steve Lutzke.
Each teacher and staff member receives a copy of the plan which is updated annually. Exactly one year after the Columbine incident, the school had to put the plan to use. A student placed a wired propane tank on the front stairs of the building.
It was diffused and nobody was hurt.