Peace agreements may inadvertently increase selective violence against civilians when they are incomplete in two key dimensions. First, only a fraction of the existing armed groups participates in the agreement. Second, the legitimate government fails to establish an institutional presence in the areas previously controlled by those who do participate. Under these two conditions, the resulting vacuum of power may attract active armed groups who engage in selective civilian victimization to obtain control. Studying the recent Colombian experience, we find that the permanent ceasefire declared by the FARC insurgency in 2014 led to a surge in the targeting of community leaders in former FARC strongholds, perpetrated by armed groups excluded from the peace process, with the goal of consolidating their dominance in those areas. Critically, selective victimization is attenuated by some dimensions of state capacity and exacerbated in places that are more valuable as proxied by the existence of recent land conflicts.