The data from the K-12 School Shooting Database (K-12 SSDB) of 1,544 school shootings were used to explore patterns of mass school shootings in the United States, with particular focus on the interplay between relevant predictors of these tragic events. Through a conjunctive analysis of case configurations (CACC), results from the current study show that (1) mass school shootings are relatively rare and (2) cluster significantly among two dominant situational profiles: lack of hostages, and a general absence of preplanning behaviors. Current findings are discussed in light of existing school shooting scholarship and recommendations for policy and future areas of research are offered.