For the last 40 years, the general profile of mass public shooters has enjoyed enduring consensus by experts, and as a result, it has remained static over this time. However, a recent string of mass public shootings perpetrated by “atypical” offenders bring into question the stability of the characteristics, motivations, and methods employed by these offenders. The goal of this study is to examine the stability and change of these characteristics and behaviors over the last 32 years (1984–2015). Using an open-source database, this study compares mass public shootings in 2000–2015 time period to the attacks committed in 1984–1999. The results illustrate not only sharp increase in number of mass public shootings in the last 16 years but also a significant growth in the racial heterogeneity and background characteristics of these offenders, clearly marking a departure from the general accepted profile of mass public shooters and mass murderers. The results also point to key characteristics, and behaviors that have remained static during the analysis time. Additionally, this study explores the implications these changes and stability on crime prevention strategies, as well as strategies to mitigate the lethality of these attacks.