The Party, in imitation of Mao’s cult of personality, decided it needed portraits of Pol Pot, and two of the prisoners happened to be painters. Thus they were offered the chance to paint for their lives. (On the list of those to die, next to the painter named Vann Nath, the camp leader Duch had scribbled the words: Leave for using.)
That’s how Vann Nath became one of the six people to survive incarceration at camp S-21, while all 15,000 others died. GQ has a lengthy and chilling writeup of Angkar, aka the reign of the Khmer Rouge in Cambodia, late 1970s.
Caution: Really really unsettling stuff. Evil in the truest and most complete sense.