It has also fed doubts over whether Brazil can guarantee sufficient safety for visitors during the 2014 World Cup football tournament, which is scheduled to open in Sao Paulo.
Marta Umbelina da Silva, 44, was opening the garage in her home Saturday night when two assailants shot her ten times in the back, throat and abdomen, police said. Her 11-year-old daughter screamed for help and Silva, a mother of three, was taken to a nearby hospital, but she could not be revived.
More than half of the 90 police murders this year in greater Sao Paulo have occurred in similar execution-style fashion.
The root cause is an escalating, eye-for-an-eye battle between police and a notorious organized crime group known as the First Capital Command. The violence appears to have been triggered by a drug bust months ago, and then spiraled out of control due to campaign politics and alleged police brutality, among other factors, security officials told Reuters.
In just the past week, the city has seen a high-speed chase and deadly shootout on the Marginal Pinheiros, the main highway in the financial district; the arson of several buses; and the deaths of more than 50 civilians, including a 63-year-old man who was run over when a bus driver tried to flee attackers.
The bloodshed has so far been concentrated in poorer areas and has not caused major disruptions to Sao Paulo's business community. It also has not approached the mayhem seen in 2006 when the PCC, as the crime group is known for its initials in Portuguese, effectively shut down activity in the metropolitan area of 20 million people for several days with orchestrated attacks that left nearly 200 dead.
The overall murder rate in Sao Paulo has increased about eight percent in recent months, to about 10 per 100,000 population, according to local media, meaning it is still less than half the Brazilian national average and comparable to US cities like Dallas and Boston.
Nevertheless, the violence has been an embarrassment for local and state officials as well as President Rousseff, who has struggled to contain a nationwide explosion in crack use - and related crime - in recent years.
"The state can't ignore this war anymore," Olimpio Gomes, a legislator in Sao Paulo state and a 29-year police veteran, told reporters at Da Silva's funeral on Sunday.
Conscious of the growing public outcry, Rousseff offered to send in the army, which has successfully fought traffickers in Rio de Janeiro. Sao Paulo Governor Geraldo Alckmin rejected that idea on Tuesday, saying the state's 130,000-strong police force already has enough manpower. But he accepted her offer to transfer some PCC leaders to maximum-security federal prisons, where it could be harder for them to coordinate violence.
Officials on the front line of the conflict say the bloodletting appears far from over.
"I fear there's a tremendous amount of revenge still to come," said Marcelo Alexandre de Oliveira, a prosecutor and specialist in organized crime who is investigating police murders. "These are people with nothing to lose."
Oliveira said violence intensified following the arrest of several mid-level drug dealers with links to the PCC. The group was particularly unhappy that police used surveillance video from a supermarket in eastern Sao Paulo to help nab the criminals - an apparent violation of "protocol" that the PCC felt compelled to severely punish, Oliveira said.
The PCC responding by threatening, and then killing, police officers, Oliveira and other sources said.
Several police murders were followed by a rash of civilian deaths in nearby areas in the next 24 hours. Human rights groups say the pattern suggests that in some cases, police or affiliated "death squads" are avenging their fallen comrades - a common practice in Brazil, and one that tends to enrage communities and reduce cooperation with police.
The cycle of killings has gotten progressively worse. Gomes, the Sao Paulo legislator, wrote on his blog that the PCC has ordered its associates to execute one police officer for every PCC leader who goes to jail - and two police officers for every PCC member who is killed.
The PCC has also begun accepting the murder of police officers as payment for drugs from low-level dealers, two sources with knowledge of the situation said.
The response has been complicated by national politics. Alckmin, the Sao Paulo governor, is the leading figure in the PSDB, the main opposition party to Rousseff's government. He has made the 70 percent decline in Sao Paulo's murder rate over the past decade one of his signature issues, and stated on Oct. 1 that the PCC is the subject of considerable "myth."
One source told Reuters that Sao Paulo officials were hesitant to ask for federal help prior to the second round of nationwide mayoral elections on October 28, in part because of concern that accepting a "bailout" on security could damage PSDB candidates in those and future elections.
A spokesman for Alckmin did not respond to multiple requests for comment.
Rousseff has not escaped scrutiny either. Federal spending on security fell 21 percent in 2011, the first year of her government, according to a study released Tuesday by Brazilian Forum on Public Security, a non-profit group.
"These police are vulnerable because they have few resources ... and we have a state structure that lets criminals walk out of prison," said Oliveira, the prosecutor. "It's a tragedy."
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