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 rare and cluster significantly among dominant situational profiles, defined by the unique combination of variables attributes; (2) mass school shootings are never pre-planned and in no case involve hostages. Current findings are discussed in light of existing school shooting scholarship and recommendations for policy and future areas of research are offered.