By Steve Kingstone
BBC News, Sao Paulo
On Monday night, 22-year-old Ricardo Flauzino went to meet his fiancee in Jardim Filhos da Terra, a working-class neighbourhood on the northern outskirts of Sao Paulo. She was arriving by bus, and as always Ricardo waited at the top of some steep steps overlooking the road.
Moments later he was set upon by a group of heavily-armed men, who shot Ricardo several times in the back and head. Local residents say the killers were police officers.
Police have killed 107 suspects, according to officials figures
"They were hooded and wearing dark shirts over their uniforms," says a 35-year-old man who, like everyone here, prefers not to give his name for fear of reprisals.
"After they shot Ricardo, they ran towards our houses, where people were chatting. And they carried on shooting, to scare us away." For emphasis, he points out bullet holes in the walls of nearby homes.
Residents say the assailants were then seen removing their overshirts, before returning in full police uniform, ostensibly to investigate the shooting.
"They were asking who shot Ricardo," recalls a young woman.
"But we all knew they had done it. It's not fair. He was a hard-working boy and was due to marry in July."
The official police record of the incident simply states that officers were called to investigate a firearms incident while on a "routine patrol". It adds that there were no witnesses to the shooting.
In the week since the wave of violence in Sao Paulo began, the police have killed 107 suspects, according to statistics produced by the state government. By comparison, in the final three months of 2005 officers shot dead 65 people.
Human rights groups say the police are carrying out what appear to be revenge attacks, in response to the deaths of 41 officers at the hands of the First Command of the Capital (PCC), a crime faction controlled from within state prisons.
"The case of Ricardo Flauzino sounds a lot like what we had during the military dictatorship," says Denis Mizne of Sou da Paz, a human rights group that works to improve Brazilian policing.
"Military police officers would organise themselves into death squads, to resolve issues of justice by themselves."
The notorious death squads of Brazil's military era were tightly-organised and overtly political in their choice of targets.
Clearly, the climate in today's democratic Brazil is much changed, but the methods of the death squads hold nostalgic appeal for some.
Living in fear
In particular, the notion of private justice seems to draw disaffected younger officers, some of whom were barely born when democracy was restored here in 1985.
"Starting with the new constitution of 1988 police power was reduced," says a 22-year-old police investigator who refuses to give his name. With friends, he is taking part in a demonstration at the state assembly in favour of higher police salaries.
"The constitution ensured that officers weren't truly able to be police officers," the young man continues. "These days the government won't support us in facing up to crime."
Members of the group are wearing black T-shirts bearing the Portuguese phrase "esquadrao da morte" - death squad.
"They stop us investigating certain crimes and individuals," adds another member of the group, aged 24. "So we are doing it for ourselves, going after the people responsible."
Despite the sharp rise in police shootings, opinion polls suggest that a large majority of Sao Paulo residents remain more fearful of the PCC than of police officers. What concerns some observers is that those fears may lead Brazilians to endorse human rights abuses.
"Everybody is shocked with the situation and thinks the police are killing bad guys," says Davi Eduardo Depine Filho, a public defence lawyer.
"But the problem is knowing who's a bad guy and who's a good guy. Our worry is that we return to the bad policing of the past, with the applause of society."
Back in Jardim Filhos da Terra, there is little doubt as to which side instils more fear. Friends of the victim, Ricardo Flauzino, live in terror of more attacks by rogue police officers, who they say have threatened to return.
"Everyone is completely terrified," says one woman, whose daughter was caught up in the aftermath of the shooting. "After eight o'clock no-one goes on out into the street. You risk dying."