It's a question painted on walls, printed on T-shirts, shouted by activists and emblazoned on banners across Rio de Janeiro — "Quem Matou Marielle?"

Who killed Marielle?

Marielle Franco was black, gay, outspoken and raised in one of Rio's slums, known as favelas.

The city councillor was assassinated on March 14, 2018, when nine bullets were fired into her car, killing her and her driver.

She had just taken part in a round table discussion on black women in power and was a fierce critic of police violence.

On the day before she was killed Marielle Franco tweeted: "How many more will have to die before this war ends". ( AP: Ellis Rua )

Two former police officers were arrested last month in connection with her murder. Both men say they are innocent.

Her former colleague — now member of the national parliament — David Miranda is also black, gay, outspoken and raised in a favela.

He fears for his safety but is determined to carry on Marielle Franco's fight for justice.

"There's men, powerful, who killed her, because we know that they don't accept people like us in politics," Mr Miranda said.

MP David Miranda said: "They don't accept people like us in politics". ( ABC News: Greg Nelson )

A record murder rate

Brazil's high levels of violence have become entangled in a brutal political battle that stretches from the alleyways of the favelas to the halls of power.

Brazil's new right-wing President, Jair Bolsonaro, was sworn in on January 1 promising to restore law, order and family values.

The former army officer almost lost his own life to violence when he was stabbed at a campaign rally.

President Bolsonaro and his allies were backed by millions of evangelical Christians seeking a safer and more conservative Brazil.

The brutal political battles stretch from the alleys of the favelas to the halls of power. ( ABC News: Greg Nelson )

Bolsonaro supporter and member of the Rio state Legislative Assembly, Deputy Rodrigo Amorim, said radical change was long overdue.

Mr Bolsonaro's friend and new MP Rodrigo Amorim says Brazilians "want to break the system". ( ABC News: Greg Nelson )

"Today we live in terror in Rio de Janeiro. Criminal groups of drug trafficking, along with militia groups, constantly at war," Mr Amorim said.

In 2017, 63,880 people were murdered in Brazil — a record number.

In the same year more than 5,000 people were killed by police. On average, 14 people are killed by police every day in Brazil.

Mr Amorim said if armed criminals end up dead police have done their job.

"I will always be a voice defending police operations," Mr Amorim said.

'Essential services are outsourced to crime'

But critics of the government say the campaign for law and order is a distraction.

Researcher and former government advisor on public safety, Dr Jacqueline Muniz, said the government is inflaming fear to get away with unlawful killings and human rights abuses.

"It is all a bluff," she said.

"Let's say it is a bad joke intending to shift Brazilians' attention ... it is about governing with crime instead of against it."

Far from safeguarding the community, Dr Muniz said the police and right-wing militias are sometimes the biggest threat.

The militias are run by current and former police and army officers.

President Bolsonaro is facing increasing demands to his family's alleged links to the militias. He denies any connections to the alleged killers of Marielle Franco.

"Her life wasn't in vain and her death wasn't either," said Marielle Franco's widow Monica Benicio. ( ABC News: Greg Nelson )

Militias have been accused of not only inflicting violence but extorting the very communities they claim to protect.

"Armed gangs like militias ... are partners of government ... it is kind of a lease with high profit," she said.

"What is at stake is not the drugs market but essential services such as water, electricity, broadband, internet.

"Essential services are outsourced to crime through the state."

Mr Miranda, a left-wing member of Parliament, said the police and the militias are operating with impunity under the guise of the government's tough-on-crime policy.

Police and militias are operating with impunity and favela residents are being targeted, according to Professor Muniz. ( ABC News: Greg Nelson )

"This is what they wanted. They want to have power with the militias, with the police," Mr Miranda said.

"Part of the population that lives in the favelas — and they're young and black — they're the ones who are going to suffer the consequence, paying with their lives."

Living in fear

Former drug dealer Sagat B almost lost his life to the police shoot-to-kill policy.

The 40 year-old still carries a police bullet in his arm where he was shot during an attempted robbery in 2010.

He said the police are exacerbating the violence by killing rather than policing.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 2 minutes 13 seconds 2 m 13 s Sagat B explains how being shot by police changed his life

"In the world where I have lived, I learned that violence begets violence," Sagat said.

"So when you say that a good thug is a dead thug, you make it grow in the thug's heart to kill too."

Sagat is now a barber by day and musician by night.

Even though he has put crime behind him he fears the police can still take his freedom or his life with impunity.

In 2017, 63,880 people were murdered in Brazil. ( ABC News: Greg Nelson )

"I can be walking there in the slum ... and lose my life for nothing, as many have already have lost."

That's the kind of police violence Marielle Franco was tweeting about before she died.

"How many more will have to die before this war ends?" she asked.

Less than 24 hours later, Marielle Franco was dead.

This year's world-famous Rio Carnaval included tributes to Marielle Franco.

Huge colourful flags rippled in the night air with her face towering over the crowd.

A Carnaval banner carrying an image of Marielle Franco, an outspoken politician who was assassinated. Photo Greg Nelson ( ABC News: Greg Nelson )

Her name rang out in songs performed by thousands of dancers and drummers from the favelas.

Mr Miranda said Marielle Franco's death will not be forgotten.

"People around the world cry with us. Their hearts broke without even knowing her," he said.

"This is how powerful she was."