It takes a well trained mind to commit these sorts of atrocities. This sort of training is going on everyday in OUR academic institutions.
Most of the KR leadership was educated in Paris under various colonial scholarships.
Khieu Samphan presented his doctoral thesis at the Sorbonne, and it detailed the exact agricultural program to be enacted by the KR 30 years later (the program that killed several million Cambodians from starvation).
Most of them also became communists in Paris, leading us to the delightful historical footnote that the French Communist Party was founded by Ho Chi Minh during his 30+ year self-exile from Vietnam.
The KR maintained their cozy relationship with Bac Ho and the Viet Minh as they built their own version of communism in Cambodia in the 50's and 60's.