The Key Figures

Dyland Klebold and Eric Harris - The killers

Dave Saunders - A teacher who helped many students escape before being shot dead

Jefferson County District Attorney David Thomas and Sheriff John Stone - Held a press conference after the massacre to say they believed other people had helped to plan the attack

Dunblane: Two decades later

The sense of disbelief and shock still reverberate across the nation, 25 years later