Third, the school rampage shootings in particular suggest a potentially important role for some kind of mental illness in the individual as a relatively important cause of the violence. Mental illness is apparent in suicide attempts and in symptoms of depression. It is also present in the fact that the grievances that the perpetrators seemed to feel, and the targets they chose to attack, seemed incomprehensible to others in the communities in which they occurred. The exaggerated sense of victimization and the arbitrary choice of victims most strongly suggest the presence of mental illness.

The more we looked at the cases of school rampages, the more they looked like other kinds of rampages rather than other kinds of youth violence or other kinds of school violence. Given the trends in this form of violence, it also seemed important to keep our eyes open to the possibility that there were contagion mechanisms operating during that period to generate the cluster of these events observed in the United States and in the world. In undertaking the case studies, the important goal was to conduct them in ways that would reveal whether these surmises have any supporting evidence.