As the 20th anniversary of the Rwanda Genocide approaches, authorities continue efforts to track down perpetrators that fled the country after committing the gruesome crimes that left 800,000 dead, the Washington Post reported.

"In our lifetime we shall continue to pursue them, and those who come after us will continue to pursue them," Jean Bosco Mutangana, a Rwandan prosecutor who runs of the government's international crimes unit, told the Post. "You cannot have reconciliation without real true justice being done."

Rwanda marked the beginning of their week-long mourning on Monday, as they commemorate the brutal attacks by extremist Hutus on mostly ethnic Tutsis and moderate Hutus.

The ceremony began with a wreath-laying at the Kigali Genocide Memorial Center. A flame was lit at Kigali's main stadium and will burn for 100 days, which was the amount of time the genocide went on for.

While Rwanda is becoming a more advanced nation, many people are concerned with the lack of justice being served to those responsible for the genocide, prompting many comparisons for the decades-long hunts for Nazi soldiers. 

"Justice hasn't been adequate, especially at the international level," said Honoré Gatera, manager of the memorial center. "It's been really a huge failure, mainly for the survivors' community in Rwanda, to see that after 20 years there are still genocidaires around the world when the court is there for the last 19 years."

The massacre began on April 7, 1994 after a plane carrying Rwanda's Hutu president, Juvenal Habyarimana, and Burundian President, Cyprien Ntaryamira, was shot down. Within hours, Hutu militias began attacking Tutsis with guns, clubs, and machetes.

Through radio programs, the militias ordered the killings of Tutsi "cockroaches" and eventually nowhere was safe. Neighbors attacked each other, teachers killed students, and even Catholic priests and nuns ordered for people to be murdered. In some mixed-ethnicity marriages, husbands handed their wives over to be killed, the Post said. 

Despite the continued horror, many Western nations failed to intervene on time, prompting former U.S. President Bill Clinton to apologize years later. U.N. Ambassador Samantha Power, who won a Pulitzer Prize for her book on the failure of America to effectively respond to the genocide, led the U.S. delegation in Monday's ceremony.