[SS.I 4.0] This large-format (17-by-25.3-inch) poster documents two decades of attacks influenced by Columbine, arranged in a timeline format, with attack details and lines of influence illustrated graphically. The diagram portrays the apparent lines of influence from Columbine through subsequent attacks. All of the post-Columbine perpetrators included here either explicitly cited Columbine as an influence or made oral or written references that suggest it influenced their own attacks. The lines of influence illustrate links between those who were influenced by Columbine and later perpetrators whom they influenced in turn. The New York Times described an earlier version of this document: “Langman has created a mass-shooter diagram tracking the influence Columbine has had on more than 30 other rampage attacks at schools and elsewhere, from California to Germany. The diagram resembles a corporate flowchart, with lines branching out and intersecting, but all of them flowing out of two names: the Columbine killers.” This is a companion document to “Role Models, Contagions, and Copycats: An Exploration of the Influence of Prior Killers on Subsequent Attacks.”