I found this disturbing and moving an article in the Frankfuerter Allgemeine, "Deadly Neighborhood": it is a story of two men who participated in the killing. I translated some of the article:

• Laurent: “It happened so quickly. I killed, killed, killed.”


• “Laurent admitted that he killed eighteen Tutsis.”


• Laurent: “I must admit that there were many Tutsis in my neighborhood. We had no problems, they visited us, and I played soccer with the children. I killed some of them later.
”

• Laurent: “Naturally I was scared of what the man on the radio said, but I never thought that the war would reach us [in Gitarama].”


• “The mayor assembled the entire village. Together they would fight against the “cockroaches.” [Laurent:] ‘By cockroaches we knew that they meant the RPF soldiers and their accomplices. We also knew that we had Tutsi neighbors. But we did not know whether or not they were one in the same.’”


• “On April 16, the mayor dragged a young Tutsi across the roadblocks and demanded that the residents fulfill their duty to the country. People hesitated; the accused accomplice of the RPF was loved throughout the village. Then someone struck him, and others followed. First with fists, then with machetes. Laurent with a hammer.”


• Laurent: “One must respect an authority who is like an elder in Rwanda. I felt, I must accepted what [the mayor] asked of us, he is the law.”


• Olivier: “After I killed the first one, everything changed. When someone told me ‘this one must be a Tutsi’, then everything else was unimportant: he must die.”


• Olivier: “You must search, you must find, you must kill … Then when one is again at peace, one feels that the work that one must do is completed.”


• Laurent: “Soon I will speak with a judge, and then I might be able to forgive myself.”

More links:
UNICEF: Rwandan Children suffering from lasting impact
International Criminal Tribunal of Rwanda
Dramatization of the trial in Brussels (in French)
Remembering and Forgetting at the University of Butare (in french)
NPR: Recalling Rwanda's Brutal 100 Days (with links)