In this paper we examine the effects of police body-worn cameras through a randomized control trial implemented in Rio de Janeiro. The paper explores the use of this technology by police officers in charge of tactical operations and officers performing “proximity” patrolling in the largest favela of Brazil, Rocinha. The study reveals that institutional and administrative limitations at Military Police of the State of Rio de Janeiro (PMERJ) were associated with limited use of the cameras –basically officers refusing to turn the cameras on. Despite low footage, results reveal that when a police officer was randomly assigned to a BWC, this technology had a significant effect reducing the number of gunshots fired by police officers. The reduction on police lethal force is particularly strong among GTTPs, which are tactical units assigned to operations that commonly involve armed confrontations. The use of BWC among these police officers reduced their use of ammunition by more than 45%. Moreover, we find that police officers assigned to a BWC had significantly lower number of activity reports or occurrences (BOPMs). The inactivity effect is mostly driven by GPP units, which have patrolling functions and more engagement with the community. These units reduce their reported activities almost by half.