Many buses were torched in May when the PCC organised crime network launched a devastating wave of attacks on Sao Paulo, Brazil's biggest city.

Police stations also came under attack and 32 officers were killed during several days of unrest.

But the police hit back with lethal force of their own, killing 15 suspects a day at the height of the violence.

Autopsy reports showed signs of summary execution in 60%-70% of fatal shootings by police, analysts say.

Rogerio do Carmo Pereira, 24, was killed during a police raid on the Heliopolis favela.

Rogerio's widow says he was killed because he confessed to a previous arrest.

Ricardo Flauzino, 22, was killed by masked men who local people believe were police officers.

But in front of a mural depicting her son, Iracy Flauzino says witnesses are too frightened to go on the record.