Nhem En says he doesn't have nightmares, even though he photographed thousands of his own people before they were tortured to death. He must have heard their screams as they were given electric shocks, beaten with iron bars, mutilated and hacked with pick axes at the notorious Tuol Sleng secret prison of the Khmer Rouge.
'When the prisoners came to my room they were blindfolded,' recalled Nhem En, who became the Khmer Rouge's chief photographer in May 1976 when he was 16.
He was at an age when most young men were chasing girls and enjoying a carefree existence rather than being part of a paranoid, brutal regime and its horrifying experiment. Many of the guards and interrogators at Tuol Sleng were aged between 15 and 19, and like Nhem En had joined the Khmer Rouge as child soldiers at eight or ten. Most came from peasant backgrounds.
The Khmer Rouge killed 1.7 million of its own people through starvation and torture in a bid to create a peasant society free of class structures and foreign influence. Nhem En defends his participation by saying he was just a cog in that killing machine.
'The blindfold was taken off and I was not allowed to talk to the prisoner,' he said. 'The prisoner usually asked: 'Why am I here?''
Nhem En ensured the prisoners did not blink or tilt their heads in the photographs. Women, men and children were forced to stand rigidly with eyes looking straight ahead as he took their mug shots.