An enduring debate sparked by the mid-1960s mass killings of suspected Indonesian Communist Party (PKI) members is the extent to which the army or civilians were primarily responsible for the violence. This question obscures as much as it reveals: not only were both civilians and army personnel actively involved in eliminating the PKI and executing its members, they at times clashed with each other over the scope of the anticommunist campaign. I argue that due to limited resources, the anticommunist faction of the army was forced to rely on civilians to provide information, legitimacy, and manpower. This provided civilians with opportunities for score-settling and killings outside of military control and without punitive consequences. Using Yogyakarta as a least-likely case for civilian initiative due to the timing of the killings, and its lack of both preexisting militia and prior intergroup violence, I argue that the degree to which the army was forced to rely on civilian communities has been overlooked as an explanation for both the scale of arrests and the number of public-spectacle killings.