The memory of the 57 killed since August 2012 is preserved with a list kept by human-rights campaigners — some by full name, others by their street monikers: Hummingbird, Woodpecker, Cinnamon. The youngest was 13, the oldest 52.

The deaths have equaled about one in 20 of the city's homeless population. In the two-year period, homeless people in Goiânia were murdered at a rate roughly ten times higher than in the rest of Brazil, although experts warned of the difficulty of gathering complete data.

After midnight on the streets of the city’s industrial core, outside its ubiquitous rodeo bars and shopping malls, the homeless stumble down the sidewalks with ripped clothes, bruised skin and panic in their eyes.

Many who live on the streets sleep during the day and walk at night. It is safer that way. In Goiânia, a city where, as one drifter put it, “no one sees and no one knows,” only the bravest dare to ask who is doing the killing and why.

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Even in a country as nonchalant about violence as Brazil, the case started to attract notice. Brazil’s federal human-rights secretariat sent a team to Goiânia to investigate. Court documents obtained by Al Jazeera America show that the secretariat identified a culture of “institutional violence” within the military police and suspicion over a series of cases that included deaths dating from 2005.

“The situation in Goiás has been alarming for years,” says Marcelo Murteira de Salles, a spokesman for the secretariat. “With the apparent involvement of military police and the delay in an effective response, it could be concluded that the state has not fulfilled its role.”

Citing the “extermination of the homeless population in Goiânia,” Brazil’s then general prosecutor, Roberto Gurgel, petitioned the Superior Court of Justice to have the investigation taken from the local detectives of the civil police, who concentrate on criminal investigations, and given to the federal police, whose officers fulfill a role similar to the FBI’s.

But 17 months later, a decision by the judge in the case, Jorge Mussi, is still pending. In the meantime, more people were killed, including four in April of last year. Then, according to records kept by the civil police, the number of murders sharply declined to 11 the rest of that year and four so far in 2014.