For 30 years Mukarumongi-Gauthier, 69, and Alain Gauthier, 75, have dedicated much of their spare time and now in retirement to trawling parts of Rwanda searching for evidence of ex-killers, prisoners and survivors.
"When we've spotted the killer in France, we go to the scene of the crime," Mukarumongi-Gauthier told the French pupils. "We look to see if there are survivors and we begin the investigation."
Ahead of the 30th anniversary of the genocide beginning on Sunday, the couple addressed around 100 high school students in the northern French city of Reims.
Known as the Klarsfelds of Rwanda after the Nazi hunters Beate and Serge Klarsfeld, the couple have made it their life's duty to "end impunity" of those responsible.
Over 100 days between April and July 1994, more than 800,000 minority Tutsis and moderate members of the Hutu majority were killed, in massacres orchestrated and inflamed by the authorities.
Rwandan-born Mukarumongi-Gauthier’s own life was utterly devastated. In late February of that year, she went to Kigali to see her family. Tensions were already high and Hutu militiamen were stationed in the capital.
'Abyss' of pain
Her mother urged her to flee to France but she could not persuade her family to leave, she told AFP, her face bearing traces of the enduring pain three decades on. She would never see them again.
Her mother, Suzana, was shot outside a church in a Kigali parish where she had taken refuge. Mukarumongi-Gauthier lost as many as 80 family members, with no survivors on her mother's side.
"It's an abyss -- all these deaths that inhabit us," she said.
For several years, the Gauthiers have gone into schools and universities in an effort to pass on the memory of what happened.
The Reims students listened to the horrific testimony of survivors, viewed archive images and watched a film showcasing Gauthiers' work.
Abylou Taiclet-Andre, 18, said it had made all the difference to their understanding, as in school they just learned figures and it remained "vague."
"Whereas here, we had people who could bear witness and we had very touching witness accounts," she said.
'Complacency'
Rwanda has long accused France, which maintained close relations with the then Rwandan Hutu-dominated regime, of complicity.
In 2021, a commission of historians set up by President Emmanuel Macron concluded that France had "heavy and overwhelming responsibilities" for the tragedy.
This week, Macron said ahead of the anniversary that France and its Western and African allies "could have stopped" the genocide but did not have the will to do so.
Historical links between Paris and the regime of then, Rwandan president Juvenal Habyarimana — whose death sparked the violence — helped many of those responsible find refuge in France after 1994, the Gauthiers say, lashing out at French "complacency."
They became doctors, priests, municipal employees and led anonymous lives.
The Collective of Civil Parties for Rwanda, which the Gauthiers co-founded in 2001, is behind the bulk of more than 30 legal cases filed in France against Rwandan nationals.
To date, seven men have been sentenced in France for their participation in the genocide, to sentences ranging from 14 years in jail to life imprisonment.
France is, along with former colonial power Belgium, the European country from which Rwanda has urged the most extraditions of suspects -- 42.
France's highest court has consistently opposed extradition to Kigali on the grounds that the crime was not on Rwandan statute books at the time of the massacre.
'Our duty'
The Gauthiers have traveled to Rwanda three or four times a year, shrugging off sleepless nights haunted by witness accounts of the horror.
"Fortunately, we did this work for the sake of justice," Alain, a French-Rwandan national, said.
"Had we not committed ourselves, I think that no genocide perpetrator would have been tried and convicted today in France.
"It is regrettable that this justice system has relied for so long on the initiative of a few basic citizens like us... It was not until 2019 that the prosecution took the initiative to prosecute and open judicial investigations against people suspected of having participated in the genocide," Alain notes..
Mukarumongi-Gauthier believes that "justice allows you to mourn." "What we do with a trial is rehabilitate victims, say their names and what they were," she said.
"This is the moral restitution the victims expect" and require, she added.
Given that countless victims ended up in mass graves and remain unidentified "their only grave... the only worthy burial we can offer them is justice" itself.
"These trials had to take place in order to strip away impunity," she said.
The couple are due to attend the commemoration in Kigali on Sunday, an event Mukarumongi-Gauthier says is important for those born after the genocide.
"We remember in our hearts almost daily. We have been living with this for 30 years," she said emotionally.
But, says Alain, "we will have done our little bit towards reconciliation in Rwanda. We did our duty."
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