Although the security situation is returning to normal, conditions that led to the riot are unlikely to improve, making a similar outbreak of violence almost certain.

A 2005 Amnesty International report claims that Brazilian prisons suffer severe overcrowding, unsanitary conditions, riots, prisoner-on-prisoner violence and the systematic use of torture and ill-treatment against prisoners by guards. Conditions such as these in the Taubaté Penitentiary led to the establishment of an inmate gang in the early 1990s known as the Primeiro Comando da Capital, or First Capital Command (PCC). In the past, the PCC has demonstrated an ability to launch multiple simultaneous attacks against law enforcement targets spread across large areas outside of prison walls.

In Brazil, as in other countries in the developing world, gangs that form in prisons are capable of exerting influence on the outside. In Mexico, Osiel Cardenas allegedly has been running his Gulf drug cartel, which is at war with the Sinaloa cartel, from prison since his arrest in 2003. The Mara Salvatrucha gang network has the run of prisons in El Salvador, Guatemala and other Central American countries.

The disturbance in Sao Paulo began May 12, the day authorities planned to transfer several hundred imprisoned gang members and leaders to a more remote, higher-security facility. The move was an effort to take the prisoners out of circulation following the discovery of a PCC plot to stage a statewide revolt. Before the transfer could begin, PCC gang members on the outside launched an offensive meant to disrupt or prevent the transfer, staging bombings, sniper attacks, ambushes and drive-by shootings. The offensive was set to coincide with prisoner revolts in more than 20 facilities, where PCC members took hostages. The uprising, in other words, was planned in advance and well-organized, and gang members were able to coordinate their actions and communicate by sending text messages over their cell phones. This prompted Brazilian authorities to jam cell phone signals in central Sao Paulo, which disrupted communications between gang members, as well as ordinary citizens.

Rampaging gang members engaged Sao Paulo police in firefights, set buses on fire and shot at banks. Public transportation in the city was virtually paralyzed, and many schools were closed. By May 14 the gangs had extended their offensive beyond Sao Paulo state, setting almost 100 buses on fire and attacking subway stations and banks, including Bank of Brazil and Bradesco Bank branches, with Molotov cocktails. Before the revolt was over, it had spread to more than 70 detention facilities across Sao Paulo state. The fighting and rioting sparked similar incidents in other Brazilian cities, though police were able to contain these less-organized outbreaks.

The large disparity between the rich and poor in Brazil, combined with institutionalized corruption and an ineffective criminal justice system, contribute to the conditions that allow these gangs to form and thrive inside and outside of prison walls. The favelas,
slums that have sprung up on the outskirts of Brazil's major cities, constitute a fertile breading ground for heavily armed criminal gangs, which on occasion have attacked Brazilian military armories to acquire weapons.

The conditions that led to the creation of the PCC and other gangs in Brazil's cities are unlikely to change in the foreseeable future. In the past, gunfights between gangs and police have occurred in the favelas, and gangs have conducted offensives against police stations and seized prisons. This was the first time, however, that widespread, sustained fighting occurred outside of the city's slums. With conditions as they are in Brazil -- both inside and outside of prison walls -- events like this are likely to be repeated.