G1 reported that the couple were navigating using the Waze cellphone application, which sent them to a street within the favela that shared a name with the road they were looking for. They planned to meet their daughter for pizza in a nearby beach-side suburb.
Waze said it was "very sad" about the incident and will meet Rio authorities this week to discuss what they are doing about the risks of driving in the city. "It is difficult to prevent drivers from navigating to a dangerous region if this is the destination selected because people who live in these areas need to get home," a spokeswoman said in an e-mail.
There have been a number of similar cases – in August, G1 reported a narrow escape for actor Fabiana Karla, whose car was also shot at after her GPS accidently sent her into the same favela – Caramujo, in Niterói, a city just across the bay from Rio de Janeiro.
56,000 people are murdered every year in Brazil, according to 2012 figures from the annual Map of Violence produced by the Latin American Faculty of Social Sciences. Even so, Saturday's shooting has generated widespread horror, shock and revulsion.
Many in this family-orientated culture were moved by the tragedy that befell what media accounts described as a loving, long-married couple who had blundered into the wrong place. Others were sickened by more violence, or sought to appoint blame.
Favelas came under the spotlight. In Rio, 1.4 million people live in these informal communities, over a fifth of the population, according to a 2010 government census. GPS applications like Waze are widely used in sprawling, chaotic Brazilian cities like Rio but they do not denote areas of risk. In August, Google maps directed this reporter into a favela in São Luís, a city in northeast Brazil, because a small street there had the same name as another road.
Many favelas in Rio are controlled by heavily-armed drug gangs who fight turf wars over lucrative territory. Since 2008, dozens in Rio have been pacified in a controversial policy that involves installing armed police bases -- often following a military occupation.
Commenting on Twitter, Rodrigo Neves, mayor of Niteroi, argued that Rio's pacification policy had prompted criminals to migrate to his city, which has not benefited from the policy.
More than 500 commented online on a G1 news story on the shooting. “The majority of favela residents are honest workers who are obliged to live with criminality,” posted one identified as Petro Neto.
“The only forbidden thing in these communities is for the police to go in and shoot crooks,” retorted another identified as Alexandre Freitas.
In fact, Brazil’s police have a lethal reputation -- especially in favelas. From January to August 2015, 459 people were killed by police in Rio alone, an 18 percent increase over the same period of 2014, according to Rio state government figures.
Many of these killings take place in favelas. Human rights campaigners say many are executions. Last week, cellphone footage shot by a resident after a 17-year-old called Eduardo Victor had been killed in the central Rio favela of Providencia caused widespread outrage. In the video, police appeared to doctor the scene of his death to make it look like he died in a shootout -- one officer secured a gun in the dead boy’s hand and fired it twice. Another video, released later, appeared to show the youth selling drugs.
“Extrajudicial executions by police contribute to the violence rather than curbing it,” wrote Maria Canineu and César Muñoz from the group Human Rights Watch in an opinion piece on Monday for Rio newspaper O Globo.
Many terrified Brazilians would disagree. In a poll by the Datafolha polling Institute released Monday, 50 percent said they agreed with the notorious yet widely used Brazilian catch-phrase: “A good crook is a dead crook.”