Two police officers were arrested Tuesday in the killing of Rio city councillor and black gay rights activist Marielle Franco, prosecutors said, almost a year to the day after the brazen murder shocked Brazil.

Franco, 38, grew up in a slum and went on to become a charismatic defender of the poor and the LGBT community, and an outspoken critic of police brutality.

She was killed in a drive-by shooting along with her driver, Anderson Gomes, in downtown Rio de Janeiro on the evening of 14 March 2018.

Her death triggered protests around the world and mass demonstrations in Brazil, but there had been little sign of progress in the murder investigation before Tuesday’s arrests.

“Two days before the anniversary of the death of my daughter, it is a consolation to know the police have arrested suspects. It was high time to get an answer,” Franco’s mother, Marinete Silva told the G1 news site. “Now we need to know who ordered it,” she added.

A sergeant in the military police, Ronnie Lessa, 48, was arrested on suspicion of being the shooter, the Rio prosecutor’s office said in a statement.

He was taken into custody at his home, a luxury seaside residence in Barra de Tijuca, an upscale Rio neighbourhood.

Elcio Vieira de Queiroz, 46, who had been sacked from the military police, also was arrested in a pre-dawn operation that was broadcast live on television.

Weapons and documents were recovered in the raid.

He is suspected of driving the vehicle that tracked Franco after she left a meeting with political activists.