MBYO, Rwanda (AP) — Twenty-five years ago, Tasian Nkundiye murdered his neighbor with a machete.

The 43-year-old Hutu and a few other men from his Rwandan village chopped the Tutsi man to pieces — one horrific slaying during a 100-day genocide that killed an estimated 800,000 ethnic Tutsis and the Hutus who tried to protect them. Nkundiye was convicted of the killing and other crimes and spent eight years in prison.

Today he lives near the widow of the man he killed. And somehow they are friends — their children and grandchildren play and share lunch together, their cows graze in the same fiel...