The Guardian offers details): the local drug gang boss tried to flee the favela in the trunk of a car. And his bodyguards apparently told the cops they were African diplomats.
According to the article, police claimed that Nem's drug trade in Rocinha involved "200 rifle-toting soldiers who were responsible for selling some 200kg of Bolivian cocaine a month" and brought in an annual fortune of around $57 million.
Of course, my time in Rocinha was a decade back, so I can't really talk about current reality (though, given what I've read about recent coke busts, the value given seems absurdly high.) But, a friend has pointed out that the police are about to occupy Rocinha in a highly publicized putsch, which probably means that the local cops were no longer going to be able to take their traditional pay-offs from the drug lord. Add to this the fact that Rio is desperately trying to clean its image in preparation for the World Cup and the Olympics, and the bust seems like a pretty shrewd PR move.
If anyone from Rocinha reads this, please let us know what's going on.