Kang Kek Iew
After the Khmer Rouge captured Phnom Penh in April 1975, Son Sen was appointed Deputy Prime Minister with responsibility for Defense. Responsible for internal security, he also oversaw the "Santebal" – the Khmer Rouge secret police. As such he monitored the operations of the infamous S-21 prison at Tuol Sleng, and engaged actively in the design of its interrogation and torture procedures. Son Sen's role meant that he was particularly closely implicated in the many thousands of deaths that occurred in this period due to the arrest and execution of perceived enemies of the regime. His memoranda to his subordinate Kang Kek Iew, and notes taken during study sessions overseen by Sen for S-21 cadres, reveal his continued interest in history, deeply anti-Vietnamese views, and revolutionary zeal, along with a "schoolmasterish attention to detail". These were combined with a brutally ruthless streak; Sen was reputed to have once been so angry with Foreign Minister Ieng Sary that he unsuccessfully attempted to have him murdered.