The mass murderer is known by a variety of names in both public and academic spheres, from the family annihilator to the active shooter, from the workplace avenger to the rampage school shooter. Although most researchers acknowledge that the phenomenon is heterogeneous, mass killing has defied classification, and currently no consensus typology exists. Most previous efforts at developing a classification scheme have focused on sorting these multicides into three broad groups, namely, family, felony, and public mass killings, exclusively relying on qualitative methods and case-study analysis to do so. The present study employs a multivariate approach to examine differences among types in victim, offender, and incident characteristics on the population of all mass murders in the United States from 2006 to 2016.