As mass shootings continue, the need for more theoretically driven solutions grows. Criminologists can offer tremendous insight, though they should be wary of applying existing theories to this relatively new phenomenon. In this dissertation, I explore how mass shootings fit into our understanding of crime and violence. I begin by describing mass shooter demographics and motives over time. I then compare mass shooters to homicide offenders and violent extremists. Focusing on social control and general strain variables, I find that mass shooters are significantly different than single-victim homicide offenders in terms of common correlates of crime. Mass shooters and violent extremists, on the other hand, show fewer differences and greater definitional overlap. Finally, I consider how mass shooting definitions shape our perception of mass shooters. Considering these results, I conclude that a mass shooter’s path to violence does not resemble that of a common homicide offender but rather one of a violent extremist. Future scholars can thus reimagine existing criminological theories to help explain mass shootings and provide solutions that are more appropriate.