Tens of thousands of people in Rio de Janeiro and other cities across Brazil have taken to the streets to mourn a murdered politician who had campaigned against police brutality.
Marielle Franco, a 38-year-old Rio city councillor, was viewed by many as a champion of women's rights.
Ms Franco and her driver were both shot dead while in her car on Wednesday.
Brazilian President Michel Temer called her murder an attack on democracy and the rule of law.
Public Security Minister Raul Jungmann has said the federal government will use all resources available to find her killers.
"I'm here at the request of President Temer," he said at a press conference.
"I would like to tell the friends of relatives of Marielle that we will find those responsible and punish them for this barbaric crime," Mr Jungmann added.
"Justice will be done."
Ms Franco was returning from an event encouraging black women's empowerment in central Rio when a car drew alongside hers and nine shots rang out.
She and her driver, Anderson Pedro Gomes, were both killed, and her press officer, who was sitting in the back seat of the car, was injured.
Police officials said it appeared Ms Franco had been deliberately targeted.
She was shot four times in the head, and three bullets hit Mr Gomes.
Ms Franco was elected to the city council in 2016 and presided over the women's commission. She was a councillor for the left-wing Socialism and Liberty Party.
Last month, she was chosen to be the speaker of the commission overseeing the deployment of federal security forces into Rio's favelas.
President Temer deployed the military in the state of Rio in February after a spike in violent crime during carnival.
The measure was approved by Brazil's Congress but has stirred controversy with some residents complaining about harassment.
Ms Franco, who grew up in Mare, a favela complex in the north of the city, has been an outspoken critic of the move to deploy the army and the federal police force.
On Tuesday, she posted on Twitter about the killing in the Manguinhos favela of a 23-year-old man, which the youth's family blamed on the military police.
"Another killing of a youth which could end up on the PM [military police] tally. Matheus Melo was leaving church. How many more will have to die before this war ends?" she asked.
Mais um homicídio de um jovem que pode estar entrando para a conta da PM. Matheus Melo estava saindo da igreja. Quantos mais vão precisar morrer para que essa guerra acabe?
— Marielle Franco (@mariellefranco) March 13, 2018
End of Twitter post by @mariellefranco
In another tweet she expressed her solidarity with the people of the favela of Acari.
"What is happening now in Acari is absurd!" she posted. "The 41st battalion of the military police is known as the battalion of death. Enough of trampling all over the population! Enough of killing our youth!" she wrote, adding a picture with the words "We're all Acari, stop killing us!"
The UN Human Rights Office in Geneva condemned the "deeply shocking murder of a well-known human rights defender" and called for a "thorough, transparent and independent" investigation to be carried out as soon as possible.
Amnesty International urged that the investigation be rigorous and focus on "the context, motive and responsibility" for the killing.