We examine discrimination against outgroups in the context of the December 2008 riots in Greece after the killing of a 15-year-old student by a special police agent. We examine students’ allocations between themselves and others, including police, in modified Dictator games, allowing us to test theories of discrimination on behavior with real payoff consequences. Treatments examined the effect of in-group norms and environmental cues on discrimination. We find that cues in the environment increase discrimination. However, contrary to existing research, in-group norms do not increase discrimination. We also correlate discrimination with attitudes towards the riots themselves, providing a laboratory test of the “frame alignment” theory of mobilization. Laboratory behaviour was correlated with self-reported participation in demonstrations, supporting the external validity of our measure.