The reflection of a visitor is superimposed over a display case containing snapshots of Khmer Rouge guards, interrogators and other workers at the Tuol Sleng prison in Phnom Penh, Cambodia. More than 1,700 people worked at the prison, codenamed S-21, during the Khmer Rouge regime of 1975-1979. Most of them were between the ages of 14 and 19 years old. During this time, an estimated 17,000 people passed through Tuol Sleng where all but a handful were murdered after months of brutal interrogation. March 1, 2012.