When French police arrested Félicien Kabuga at his flat on the outskirts of Paris on Saturday, it ended 26 years on the run for one of the key figures behind the Rwandan genocide.

Neighbors said they barely knew the 84-year-old who took daily walks but rarely spoke to anyone. They described him as frail and said he had lived in Asnières-sur-Seine, a well-to-do suburb, for at least four or five years. They did not know his name, but it was fake anyway.

Behind this quiet facade was a man with a 5-million-US-dollar bounty on his head, wanted by a United Nations tribunal for financing and facilitating the killing of more than 800,000 people.

100 days of terror

The Rwanda genocide horrified the world in 1994, coming on the back of ethnic cleansing campaigns and massacres in the conflict-torn former Yugoslavia.

Over three months from April to July, some 800,000 Tutsis and moderate Hutus were killed, many hacked to death by machetes, in one of the worst examples of ethnic violence on record.

There had long been tensions between majority Hutus and minority Tutsis, but the shooting down on April 6 of Rwandan President Juvénal Habyarimana's plane, killing him, lit the fuse.

Communities, neighbors and families turned on each other. Militias, known as Interahamwe, went around slaughtering people and put up roadblocks to catch more victims in a well-orchestrated killing campaign. They were egged on by the now infamous Radio Mille Collines, which spewed hatred over the airwaves, broadcasting hit lists and directing militias on where to find Tutsis.

'Mastermind' of the genocide

Kabuga, a Hutu businessman, was one of Rwanda's richest men at the time and an influential figure with close family links to Habyarimana. Not only did he finance the genocide, he played an active role in it, according to the indictment against him.

Kabuga helped set up a National Defense Fund "in order to raise funds to provide financial and logistical support for the Interahamwe's killing and harming of Tutsis," the indictment by the International Criminal Tribunal for Rwanda (ICTR) reads.

He supported the militias by "issuing them weapons and uniforms and by providing them transport in his company's vehicles," the U.S. State Department said in a note offering a 5-million-U.S.-dollar reward for information leading to his arrest.

An earlier version of the UN indictment said he ordered large imports of machetes which were then distributed to the Interahamwe.

Kabuga also controlled Radio-Mille Collines – whose hate-filled broadcasts described Tutsis as cockroaches and encouraged listeners to "cut them down" and "make them suffer" – and he "instructed" and "prompted" Interahamwe in the killing of Tutsis, the indictment says.

As early as February and March 1994, he is alleged to have "incited genocide or made persecutory statements" at meetings around the country.

On the run

Kabuga fled to Switzerland in June 1994 but Swiss authorities failed to arrest him. He was then found to be living in Kenya in the late 1990s, but again escaped arrest.

When he arrived in France and how he entered the country is unclear.

The Paris prosecutor's office said that over the past 26 years, Kabuga had "stayed with impunity" in Germany, Belgium, Congo-Kinshasa, Kenya and Switzerland.

This was despite an Interpol Red Notice being out for his arrest.

In 1997, the ICTR indicted him for his role in the Rwanda genocide. The charges include five counts of genocide, incitement and complicity in genocide, and two counts of crimes against humanity.

Bringing the perpetrators to justice

The ICTR – based in Arusha, Tanzania – was the first international tribunal to deliver verdicts in relation to genocide. From 1995 until its closure in 2015, 93 people were indicted and 62 sentenced, including military and government officials, businessmen and religious, militia, and media figures.

Community courts in Rwanda also prosecuted over 1 million lower-level perpetrators, according to media reports.

Kabuga was among eight fugitives still being sought internationally in connection with the Rwanda genocide. But he was one of the biggest fish in the group, alongside Augustin Bizimana, Rwanda's minister of defence at the time of the genocide, and Protais Mpiranya, who was the commander of the Rwandan Presidential Guard.

Bizimana, now 67, is wanted on 13 counts of genocide, crimes against humanity and other violations, including murder, rape and torture. Mpiranya, about 60, has been indicted on eight counts of genocide, crimes against humanity and other violations, including for the killing of Rwanda's Prime Minister Agathe Uwilingiyimana and 10 Belgian UN peacekeepers in the opening days of the genocide.

As with Kabuga, huge rewards have been offered for any information leading to the arrest of both men. Their whereabouts, or even whether they are still alive, are still unknown however.

Questions remain

While rights groups and survivors' associations welcomed Kabuga's arrest, questions remain about how he could have evaded justice and found refuge in France for so long.

The Paris prosecutor's office said he settled in Asnières-sur-Seine with the help of his children. But others have criticized that dozens of alleged perpetrators, including Agathe Kizanga, Habyarimana's widow, have been able to live in France undisturbed for years. A Rwandan extradition request for Kizanga, believed to have been a key figure in power in 1994, was turned down by a Paris court in 2011.

What next?

Currently held at La Santé prison in Paris, Kabuga will first appear before a French judge before his case is handed over to the International Residual Mechanism for Criminal Tribunals (IRMCT), which took over from the ICTR after its closure.

His trial could be held in Arusha or The Hague, Netherlands.