New concerns are being raised in Brazil about the excessive use of police force against some adversaries. A video from a Rio de Janeiro police helicopter depicting the hunt for a drug trafficker has gone viral, due to police peppering the suspect's car with gunfire from the air in a densely populated residential area. The video was recorded on the night of May 11 as police attempted to track down Márcio José Sabino Pereira, a convicted drug trafficker widely known as "Mathematician," through a slum called Favela da Coréia.

His body was found in a nearby car the day after the air raid, which police described as a "resistance killing." It was not immediately clear whether other people were injured or killed in the hunt, but several buildings surrounding the vehicle were shown to be hit by the bullets. When asked about the heavy use of gunfire in a residential area, Adonis Lopes de Oliveira, the helicopter's commander, said that the street was "frequented largely by traffickers."

Legal authorities and human rights advocates expressed outrage over the excessive police force and Marfan Martins Vieira, a prominent prosecutor in Rio de Janeiro, confirmed on Monday that he would reopen an investigation into the killing. Martin Rocha, the head of Rio's Civil Police force, acknowledged that, "This image leads us to admit that there could have been a disproportionate action."

The video highlights security challenges that Rio continues to face as it gears up to host the 2014 World Cup and 2016 Summer Olympics. Crime has declined in some parts of the city, but drug trafficking organizations and militia, many of which are operated by active duty or retired police officers, still hold major influence over large areas of the city.

"The so-called pacification of Rio de Janeiro is for a certain territory that interests certain investments in the city," said Marcelo Freixo, a lawmaker and leading human rights activist in Rio. "The city of Rio is a lot larger than this, and the areas that are not part of these mega-events are still living with the kind of images you saw."