The United States has experienced a tragic increase in school shootings in recent years. Despite substantial media attention being paid to such incidents and widespread support for stricter gun control measures, substantial legislative action remains absent, however. To make sense of this puzzle, this paper focuses on the mobilizing responses of gun rights supporters in the aftermath of such events. Using granular data from 225,000 donations to the NRA’s political action committee in a difference-in-differences design, this study provides causal estimates showing substantial increases in both donation amounts and donor numbers after school shootings. These results provide insight into the counter-mobilizing responses of the pro-gun political right after shootings. In contrast to the typically transient nature of gun control movements, these counter-mobilizing responses are notably durable. The results of this study have important implications for our understanding of the complexities of, and obstacles to, gun regulation in the United States.