Two months after the Nascimento shooting, meanwhile, a separate incident drew attention to what prosecutors allege is one of the darkest sides of Brazilian police: Freelance death squads, called grupos de extermínio, in some precincts. As recently as 2010, four military police officers were sentenced to 18 years in prison for participating in one squad, which allegedly decapitated some of its victims.

Police say the death squads earn $40 to $50 for killing a street kid and as much as $500 for an adult. In January, Health Minister Alceni Guerra said the government had evidence that "businessmen are financing and even directing the killing of street children." The military police confirm this. "There are groups that are paid by businessmen to protect their shops," says Maj. Altanir Freitas. "But since the community protects these groups, it's hard to find out who they are."

Last year, according to government statistics, 492 street kids were murdered in Brazil, many of them gruesomely mutilated. Other groups, like Rio's National Movement for Street Children, say the figures are even higher. "From January 1988 to December 1990, 4,611 kids were assassinated," says Volmer do Nascimento, the group's director (and a former math teacher with a penchant for quoting statistics from memory). "That's 4.2 kids a day," he adds. "Every day. And it's getting worse."