Test the effects of a recent police stop and a recent police stop at gunpoint on changes in attitudes towards the police among residents of Brazil’s biggest city. A three-wave longitudinal survey of São Paulo residents (2015–2019) measured people’s beliefs about police legitimacy, expectations of police procedural fairness, effectiveness, and overpolicing, whether they were recently stopped by the police, and whether officers had pointed a gun at them during that stop. A novel causal estimand focused on the effect of change in treatment status is estimated using matching methods for panel data combined with difference-in-differences. While estimates are too imprecise to suggest an effect of a recent police stop on attitudinal change, recent police stops at gunpoint decrease public expectations of procedural fairness, increase expectations of overpolicing, and harm public beliefs of police legitimacy. Under a credible conditional parallel trends assumption, this study provides causal evidence on the relationship between aggressive policing practices and legal attitudes, with implications to public recognition of legal authority in a major Global South city.