The alleged killer of over 2,000 people in the Rwandan genocide of 1994 has been arrested in South Africa after two decades on the run.

Fulgence Kayishema was arrested on Wednesday afternoon in a joint operation between South African authorities and the prosecutor’s fugitive-tracking team, according to the chief prosecutor of the tribunal charged with finding the remaining fugitives.

The most wanted fugitive is said to have been on the run since 2001 after orchestrating the killing of more than 2,000 Tutsi refugees, which include, women, men, children and the elderly at Nyange Catholic Church during the genocide.

“His arrest ensures that he will finally face justice for his alleged crimes,” said Chief Prosecutor Serge Brammertz of the International Residual Mechanism for Criminal Tribunals (IRMCT).

“Genocide is the most serious crime known to humankind. The international community has committed to ensure that its perpetrators will be prosecuted and punished. This arrest is a tangible demonstration that this commitment does not fade and that justice will be done, no matter how long it takes,” Brammertz added.

The IRMCT prosecutor had previously complained about the lack of cooperation from South African authorities and there have been a series of near misses capturing Kayishema. But on Thursday, Brammertz lauded the cooperation and support of the South African government.

The genocide in Nyanga, Rwanda, were one of the most brutal in which an estimated 800,000 Tutsis and moderate Hutus were killed over the period of 90 days.

According to the tribunal, Kayishema directly participated in the “planning and execution of this massacre.” The indictment says he bought and distributed petrol to burn down the church while refugees were inside. Kayishema and others are also accused of using a bulldozer to collapse the church following the fire, while refugees were still inside.