In an attempt to capture a drug-trafficking organization's leaders, at least 21 people were killed, including one woman, and seven were injured and taken to a hospital, during a police raid on a Rio de Janeiro favela.

Residents said on social media that heavy shooting started at 4 am in a wooded area next to Vila Cruzeiro, and according to a Reuters photographer who was near the scene, gunfire began again in the afternoon.

The incident is one among Rio’s deadliest police operations and comes one year after a raid of the Jacarezinho favela that resulted in the death of 28 people, sparking protests and reigniting debate over the behavior of the police force in Rio, where a common local saying is, “A good criminal is a dead criminal.”

The police operation was targeting leaders of Rio’s largest organized crime gang, the Comando Vermelho, who were hiding in Vila Cruzeiro, as per the police intelligence. 

“It was a very intense confrontation,” the spokesman for the militarized police force that led the operation, Colonel Ivan Blaz, told reporters.

A criminal investigation was opened, the Rio state public prosecutors said in a statement, giving the military police 10 days to give details on which officials were responsible for each death and justify the use of lethal force, the statement said.

The operation was backed by a helicopter and conducted jointly by federal highway police and the military police. 16 vehicles, 13 automatic rifles, pistols and grenades were seized, the statement said.

Earlier this year, Brazil’s supreme court set a series of conditions for police to carry out raids in Rio’s favelas as a way to decrease police killings and human rights violations. According to the court, lethal force should be used only in situations where all other ways have been tried and when necessary to protect life. The court also gave police 180 days to install devices that record audio and video on their cars and uniforms.