Shooting from helicopters, armoured personnel carriers or at close range, police officers in Rio de Janeiro gunned down 558 people during the first four months of the year — the highest number in this period since the state began keeping records more than two decades ago.

This recent spike comes after years in which the federal and local authorities put in place policies that significantly diminished police killings. But as the country dove into a deep economic and political crisis in 2014, resources for security programmes dried up. Criminal gangs reclaimed lost territory in Rio, and across Brazil violence exploded: More than 51,500 people were killed last year.

Voters went to the polls in October and gave their support to candidates who promised to fight violence with violence by relaxing gun ownership rules and allowing police to fire on armed suspects.

The number of people killed by police in Rio de Janeiro jumped in 2018 to a high of 1,538, according to state statistics. If killings continue this year at the current pace — nearly five a day — that record will be beat.

The state’s newly elected governor, William Witzel, pointed to an overall drop in homicides to argue that the approach was working.

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“We’re on the right track,” Mr Witzel wrote on Twitter on Tuesday, celebrating the drop in homicides and other crimes. “We’re going to continue preserving the lives and liberty of our families.”

President Jair Bolsonaro, a far-right former army captain, had promised to give the police more leeway to kill suspected criminals, repeating a popular saying that a “good criminal was a dead criminal.”

Mr Witzel, a former federal judge, endorsed tactics that legal experts say amount to extrajudicial killings.

Soon after he was elected, Mr Witzel said police officers should be authorised to open fire on any criminal seen carrying a rifle. “The police will do the right thing: Aim at their little heads and fire! So there is no mistake,” he told a local newspaper in November.

He seemed to relish in the prospect of a rising body count, saying in January that there would be no shortage of places to send criminals. “We’ll dig graves,” he said.

In March, Mr Witzel announced that snipers deployed covertly across the state were gunning down armed suspects who “have to be lethally neutralised.”

But some local lawmakers and activists in communities that have been the targets of violent police operations say officers are routinely carrying out extrajudicial killings.

“Summary executions are being carried out in favelas and other peripheral areas,” said Renata Souza, a state representative who urged the United Nations and the Organisation of American States to investigate. “It is a barbaric state policy that amounts to genocide.”

Prosecutors acknowledge that they do not have the personnel or resources to investigate more than a small fraction of such cases thoroughly.

The state prosecutor’s office created a task force in 2015 to investigate allegations of excessive force. Since then, the police have killed more than 4,000 people in the state. The unit has charged 72 officers with homicide; of those, at least 19 have been acquitted and none are in prison.

Paulo Roberto Cunha, a leader of the task force, said his team faced a crushing workload, deficient forensic investigations and the reluctance of many witnesses who fear police retaliation.

While the police in Rio de Janeiro are required by law to record events from cameras installed in patrol cars, the devices have vanished from the vast majority of vehicles, depriving investigators of critical evidence.

In 2017, the Inter-American Court of Human Rights condemned Brazil as failing to investigate questionable police killings and ordered the country to do so.

But the stacks of case files piled up on Mr Cunha’s desk — and in filing cabinets outside his door — underscore the vastness of the challenge. There are 14 prosecutors in the task force.

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Rio de Janeiro has long been an immensely complex state to police. Dozens of districts settled by squatters decades ago, and long neglected by the state, are controlled by drug traffickers and paramilitary groups. Young men with semi-automatic rifles guard entry points to several communities. Police typically enter only to carry out raids — and often leave bodies in their wake, according to residents.

Soon after the first shots rang out in the hilly Fallet-Fogueteiro district near downtown Rio on the morning of 8 February, it became clear to residents that this was no ordinary shootout in an area where rival gangs have long fought for dominance.

As an elite police squad rumbled up the hill, passing murals that have been defaced with graffiti paying homage to a dominant drug gang, a group of suspected traffickers scurried into a house. They took their shirts off — a gesture that signalled they were surrendering, according to residents.

Among them was Felipe Guilherme Antunes. He peeled off the black T-shirt he had put on that morning, which said “Black Is Beautiful,” and waited.

By the time the hail of bullets ceased, nine men lay on the ground in puddles of blood, and four others were gunned down outside.

Police officials at the time said they were acting in self-defence. But as relatives and human rights investigators pored over witness accounts, autopsy reports and photos of the bodies and the house’s blood-splattered walls, many grew convinced that the men had been executed. None of the officers in the raid were wounded.

According to Human Rights Watch, which examined nine of the autopsies, some of the bodies had shots to the head or the heart.

“They didn’t come to take them into custody,” said Tatiana Antunes de Carvalho, the mother of Antunes, who said his wounds did not match the autopsy description. “They came to kill.”

Mr Witzel and senior state police officials turned down repeated requests for interviews. In a short statement, the Police Department said it “obeys all protocols in its actions and acts according to law, including in the realm of investigations.”

Children and other bystanders are often caught in the crossfire: In March, 12-year-old Kauan Peixoto was shot three times. In April, 16-year-old Luana Simas was shot in the back seat of a car. In May, a 27-year-old motorcycle driver was killed during a police shooting in the Rocinha district.

Empowering the police to kill more easily has never reduced violence, said Roberto Sá, who oversaw security policy in the state from 2016 to 2018 and served in an elite police unit earlier in his career.

“Confrontation generates an unsafe environment, mental illness and stress for police officers and residents,” he said.