In the spring and summer of 2020, police in the U.S. killed Breonna Taylor, George Floyd and other unarmed people of colors. Thousands across the country engaged in public protests and called to defund or abolish the police, constituting one of the largest social movements in the nation’s history. Public views on the Black Lives Matter movement are polarized along traditional political lines, and although scholars are beginning to study this phenomenon, surprisingly little empirical research has considered social identity and intergroup relations between the police and policed. This leaves a critical question largely unanswered: what roles do different types of social identification and different dimensions of justice perceptions play in explaining public attitudes towards police reform in general, and public attitudes towards defunding the police in particular? The current study builds on the group engagement model and work on public attitudes towards police activity and violence to examine the roles of social identity, inter-group relations, and perceptions of police fairness. Analyzing data from a cross-sectional quota sample survey of 1,500 U.S. residents conducted in summer 2020, our findings support the proposition that, at least at the moment just after the murder of George Floyd, support for defunding the police was related to not only political views and superordinate identification with the group that the police proto-typically represent, but also inter-group identification with the police and the Black Lives Matter movement, as well as people’s perceptions of procedural justice and the under- and over-policing of Black communities.