The Primeiro Comando da Capital, or PCC, is a very sketchy Brazilian crime organization that formed out of a prison gang in Sao Paulo. Since 1993, the PCC has orchestrated prison breaks, riots, all types of robbery, and they’re really good at drug trafficking too. Like most gangs, they have some rules, and if you don’t adhere to them they’ll kill you--that’s how it works.
Lately, the PCC has been really focused on killing cops at the request of one of their leaders Roberto Soriano, who also goes by Betinho Tirica and is serving time in prison. Roberto/Beitnho has been messaging PCC members and letting them know what cops to kill--usually because they arrested drug dealing PCC dudes. The police aren’t having it and are doing some killing of their own--they shot and killed six alleged PCC criminals in May 2012--instead of just arresting them like cops should.