Life simply stopped in the megalopolis of 18 million people around the middle of May. There was panic in South America's richest street, Avenida Paulista. More than 80 public buses were fire-bombed.
Hoax bomb threats closed the international airport and the headquarters of multinational companies, such as IBM.
The organised attacks began on 12 May in response to the transfer of 765 prisoners – members of the First Command of the Capital (PCC) gang - in an attempt to split up their leadership.
Inside the prisons there was a huge co-ordinated rebellion which affected 75 different penitentiaries in Sao Paulo. Hundreds of hostages were taken.
When Monday came around no one went to work. In the place of infamous rush-hour traffic, empty roads. Shopping centres, schools and universities closed as people stayed at home gripped by fear.
And then it stopped.
Pull back troops
In the immediate aftermath, three members of the Sao Paulo state government admitted they and military police commander Ailton Araujo Brandao visited PCC chief Marcos Willians Herbas Camacho, held in solitary confinement at the Presidente Bernades jail, urging him to end the attacks.
After commanding 251 attacks in total, Camacho, also known as Marcola, simply pulled back his "troops".
A megalopolis of 18m people,
Sao Paulo has high crime level
Although Brandao insisted no "deal" had been made, he told local media Marcola had put forward the conditions of the PCC – no police reprisals against gang members and access to hot baths, conjugal visits and TVs to watch the World Cup.
The structure of prison gangs in Brazil follows a common denominator – the "godfathers" command their troops from inside maximum security jails using smuggled "goats", slang for cloned cell phones.
They send instructions to the "pilots" who in turn mobilise the "soldiers" in the favelas.
PCC, created in 1993 after an infamous massacre of 111 prisoners by police in Sao Paulo's biggest penitentiary Carandiru, claim to have an army 10,000 strong.
The faction is estimated to have "control" of 90% of Sao Paulo's prison population which houses nearly half of the country's 336,000 prisoners.
Vicious prison system
Overcrowding and chaos in the notoriously vicious prison system and lack of security is cited as one of the prime reasons for the rise in power of the PCC.
"The tragedy is the result of a failing prison system and a deficit of 130 prisons which have not been built in Brazil. There is no doubt. Two-third of the prisoners live in precarious and shameful conditions," says Jose Reinaldo Guimareas, a specialist for the working group for the repression of organised crime.
Sao Paulo's civic society has responded with indignation at the ease at which the jailed leaders have access to cell phones.
Two-thirds of Sao Paulo's prison
population live in ugly conditions
It was revealed too that not only have they received the devices through corrupt guards but that in one case even arms had been delivered into a prison using the state postal service, Sedex.
The ministry of justice reacted by blocking the signal for mobile devices in and around six penitentiaries in Sao Paulo but the phone operators are challenging the decision.
But more significantly, gang-related violence in Sao Paulo have revealed the awesome power of its criminal gangs to shut down Brazil’s economic heartland which generates more than a third of the country's wealth.
The country is well accustomed to such actions in the more famous neighbouring city of Rio de Janeiro where factions in the drug trade regularly force the closure of main thoroughfares.
In fact, it is on an island off the coast of Rio that the biggest drug faction, Comando Vermelho (Red Command), was first established.
All that remains now of the island's Instituto Penal Candido Mendes is a facade after its demolition in 1994.
In the 1960s and '70s it housed a mishmash of writers and revolutionaries during the military dictatorship.
Comando Vermelho was a result of a marriage between the organisational skills of the revolutionaries and the criminal minds of the rest, according to legend.
Citizens are slowly picking up the
pieces of their troubled city
"It was created here in 1974. There were a lot of fights between them and a rival gang because of drugs," remembers Senhor Julho, a former inmate, who was jailed for 26 years in the notorious prison.
"There began a little part of the movement outside and then a war started between them inside. When they were created, Comando Vermelho began killing people, two or three a day, because of the movement."
Julho says he was invited into the new organisation but didn’t feel obliged to become a member.
"I said I was here recuperating and I didn't want to be part of it. We had a system where if you saw things you kept your mouth shut," he says.
Today the faction is a virtual parallel power in Rio and controls most of the territories of the giant favelas, or slums, in an undeclared armed civil war.
With only four months to go until Brazil's general election, the crisis has taken on a particular political dimension, opening a cold war between the party in control of the state of Sao Paulo, the Brazilian Social Democratic Party (PSDB), and the Workers' Party (PT), which controls the federal government.
The only contender against Luiz Inacio Lula da Silva, the Brazilian president, is Geraldo Alckmin, the ex-governor of the state of Sao Paulo, who stepped down in March to run for the presidency.
"We had a system where if you saw things you kept your mouth shut"
ex-inmate of Instituto Penal Candido Mendes facility
His vice, Claudio Lembo, who took over for the remainder of the mandate, refused federal help to quell the crisis, claiming that it was "too small and local" for the army to step in.
But later Lula offered support - in the knowledge that the attacks will have helped his expected candidacy - saying that the governor "had done all he could do".