Eight supporters of São Paulo club Corinthians were shot dead on Saturday night in the worst incident of football related violence in Brazil's history.
The victims, all members of Corinthians' Pavilhão 9 torcida organizada (organised supporters) group of ultras, were in their headquarters playing football and preparing banners for Sunday's derby against arch rivals Palmeiras when up to three armed and masked men entered the building, which is located under a bridge on one of the city's main freeways.
They ordered about 80 people present to lie on the floor and then executed seven men with shots to the head. Another man was also shot but managed to escape the building. He was taken to hospital where he died of his wounds.
Police were quick to play down immediate suspicions that the massacre was the work of Palmeiras supporters. Torcidas organizadas from the two clubs have a violent rivalry that has worsened since March 2012 when Corinthians fans ambushed members of the largest Palmeiras torcida, Mancha Verde.
One Palmeiras fan was killed in the ensuing melee and 14 Corinthians fans now face trial for his death. But they are all members of the club’s largest ultra grouping, Gaviões da Fiel, rather than Pavilhão 9.
Instead of inter-club rivalry being responsible for the massacre, police suggested a settling of accounts within the criminal underworld as a possible motive, saying two of those killed had convictions for drug trafficking.
This hypothesis is frequently used by police to explain mass killings in São Paulo. On Thursday, just hours after a police officer was shot dead, six people were killed and one injured in death-squad style attacks in the south of the city.
Authorities were quick to suggest other criminals were responsible, pointing out that three of the seven victims had criminal records. But community groups in São Paulo’s periphery say such killings are carried out by police officers to revenge murdered colleagues.
The Pavilhão 9 torcida group was founded in 1990 and is named after the notorious pavilion in Carandiru, then South America's largest prison, where in 1992 police killed 111 prisoners during a rebellion.
A formal organisation rather than a hooligan firm, it has a registered membership, headquarters and a carnival school that takes part in São Paulo’s annual parade.
Brazil’s torcidas exercise considerable influence within Brazil’s football clubs but have frequently fallen foul of authorities because of their propensity for violence against rival fans and even against other groups who support the same club.
Last year, Corinthians were ordered to play one of their home games outside of São Paulo as punishment for fighting between Pavilhão 9 and another of the club's torcidas, Camisa, 12 at their stadium.
Andrés Sanchez, one of the founders of Pavilhão 9 who went on to become Corinthians’ club president and is today a federal deputy for the ruling Workers Party, took to Twitter to express his condolences to the families of the victims.
Despite the massacre the game between Corinthians and Palmeiras was set to go ahead as planned on Sunday evening.