Today is the dead's day here in Brazil. Nice day to start posting...
That is the so called Carandiru's Massacre. Carandiru was a big prison at São Paulo City in Brazil.
It has occurred at an election day, at october 1992. There was rumors of a massive riot attempt at the prison, and several militar policeman were sent there. But the prisioners apparently were not doing that, and were executed by the policemen. 111 men died.
Until now there was no punishment for anyone. Coronel Ubiratan, the head of the militar policemen at that day was found dead at his home some years later. The prison inspired a book and a movie. Carandiru was destroyed and now a park exists in this area.
This is the best picture I have found at Internet. Does anyone have more?