This Thursday will mark a year since my friend and colleague Marielle Franco was assassinated. The execution of an elected politician and human rights activist in the city of Rio de Janeiro highlighted just how tightly interwoven crime and politics have become in one of Brazil’s main cities.

According to the NGO Global Witness, more human rights activists are killed in Brazil than anywhere else in the world – and this at a time when our country is once again showing a decline in social indicators. At times like these, human rights defenders are figures we must treasure.

Marielle was executed by a group known as “The Crime Bureau” – a shadowy and elusive organisation which commits murder at the bidding of politicians, criminals, right-wing paramilitary “militias” – and whoever else has a few hundred thousand reais to pay for the murder of someone they don’t like.

This time, they killed a noble woman who stood up for the best of causes – an activist who put her life and political power at the service of those who have been historically oppressed in a society beset by profound inequality.

Beyond knowing who pulled the trigger of the weapon which killed Marielle, we must know who ordered the crime

During investigations into Marielle’s murder, there were strong signs that powerful forces were acting to prevent the solution of the case. Then the Federal Police probed the conduct of the Civil Police – an investigation of the investigation – and the case took a different direction. The arrest on Tuesday of the two men suspected of carrying out the murder, was part of that shift.

It is crucial that the case is solved in order to stop any more attacks on the fundamental rights of the most vulnerable members of our population – and to ensure that politicians can continue doing their job in Brazil

That is why, beyond knowing who pulled the trigger of the weapon which killed Marielle, we must know who ordered the crime.

The close ties between illegal militias and politicians in Rio de Janeiro represents an extraordinarily serious breach of our democracy. In the hours that followed the arrests of the alleged killers this week, a photograph began to circulate on social media showing Brazil’s president, Jair Bolsonaro, embracing one of the those men.

On its own, this does not prove any link between the president and his family and Marielle’s murder. But the ease with which a photograph showing Bolsonaro with a militia member was found is extremely troubling.

When the president’s eldest son, Flávio, was a state deputy in Rio, he employed the wife and the mother of a fugitive former policeman who has been accused of running the Crime Bureau.

Finding out who ordered Marielle’s murder is key to the most important political cause of our time: stopping authoritarianism in Brazil. With that comes the possibility of a democratic movement which can help us overcome the current state of affairs.

The arrest of the two alleged killers was a belated, but crucial first move. Now, the next – and far more important – step must be taken. This case will not be closed with the arrest of whoever pulled the trigger.

For the past year we have asked two questions again and again.

One of those questions may have been answered. But the other remains unresolved: who ordered Marielle Franco’s murder?