Authoritarian regimes frequently commit systematic killings of their own subjects, yet the mechanisms governing this behavioral shift remain unclear. We address this puzzle by developing a formal model that shows authoritarian elites perpetrate systematic killing campaigns preemptively in response to an exogenous shock where urban development levels are sufficiently high. In these contexts, the civilians cannot commit not to mobilize and pose a credible threat to the regime, which often preempts these efforts using systematic killings. Statistical analyses of a global high-resolution sample within all authoritarian states between 1996 and 2008 confirm the model’s predictions. This study thus explicates when elites would resort to systematic killing as a rationalist strategy, and identifies an important dynamic that explains geographical and temporal variations in systematic killings within authoritarian states.