Maraunding mobs killed in the neighborhood of 800,000 people over three months in Rwanda.
It doesn't seem much of a stretch at all for one of thoe most elite, fearsome fighting forces in the history of man, made up of warriors who trained rigorously since childhood, who conquered essentially all of the known world at the time, to have killed over 60 million (by some estimates over 100 million) over a period of 8 years.
They'd have to manually kill each and every one.