Following a coup in Indonesia in the 60's, right-wing death squads killed a million or so "communists" - those death squads then evolved into a paramilitary organization with current ties to the government. In the course of filming a movie ("The Act of Killing") about the mass killings, the director wound up asking the perpetrators of the killings to act out their recollections of the events on camera, and they were happy to do so.
Wikipedia article about the mass killings
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