A police operation Thursday targeting gang members in Rio de Janeiro’s largest complex of favelas, or low-income communities, left at least 18 people dead in one of the deadliest raids the city has seen recently and one already bringing more criticism of police violence.

Rio authorities said 16 suspected criminals were killed in confrontations with police in Complexo do Alemao along with a police officer and a woman. A police spokesman said the raid targeted a criminal group that stole cars and robbed banks, and invaded nearby neighbourhoods.

Videos circulating on social media showed intense shootouts between criminals as well as a police helicopter flying low over the small, brick houses. Rio’s police have used helicopters to shoot at targets, even in densely populated residential areas, and video showed shots being fired from the favela at the aircraft.

At the site of the raid, Associated Press reporters saw residents carrying about 10 bodies as bystanders shouted, “We want peace!” Residents said those who attempted to help the injured risked arrest.

“It’s a massacre inside, which police are calling an operation,” one woman told AP, speaking on the condition of anonymity because she feared reprisals from authorities. ”They’re not letting us help (victims),” she added, saying she saw one man arrested for attempting to do so.