This is an exploration of the issue of influence among school shooters, documenting references by subsequent attackers to those who came before them. It also notes historical figures who may have served as role models for violence. The bulk of the document is a listing of school shooters and their influences, including a diagram of the lines of influence from Columbine through subsequent attacks. For an analysis of the multiple types of influence among school shooters, see the document “Different Types of Role Model Influence and Fame Seeking Among Mass Killers and Copycat Offenders.” For a graphic representation of the influence of Columbine on subsequent attacks, see “The Influence of Columbine” (poster and tabloid format).