Perceptions of injustice are central to fueling violent political action, though not everyone within a social movement will support violence in response to collective grievances. So who supports violence and who doesn’t after perceived injustice? To address this question, we followed up on the same individuals (N = 805) before and after a court decision in Catalonia (Spain) sentencing nine separatist leaders to prison, an event that led to mass violent and nonviolent protests. We tested three hypotheses by combining classical theories of collective action and more recent extremism models and found support for all three hypotheses. Namely, individuals who exhibited steeper increases in radicalism (controlling for activism) after the court ruling were those who had previously experienced police violence (social dynamics hypothesis), those who identified as separatists (separatist identity hypothesis), and those who held Catalan independence as a sacred value (sacred value hypothesis). Our findings offer a complex picture of real-world conflict settings, where the three evaluated factors seem to be intertwined. We discuss potential venues to restore inter-group relations after perceived injustice, with an assessment of how likely these strategies are to succeed based on the three adopted perspectives.