On January 10, 1979, Vietnamese photographer Ho Van Tay discovered human remains at the former Tuol Svay Prey High School in Phnom Penh, Cambodia. The Vietnamese Army had invaded Cambodia weeks prior and entered the capital days earlier.
The city of Phnom Penh, previously home to three million people, had been evacuated by the Khmer Rouge regime in 1975 as part of its agenda to establish an agricultural collective. The high school had been converted into Security Prison 21, also known as S-21, serving as a prison and interrogation center.
Upon discovery, the site contained only decomposing bodies. Ho Van Tay documented the findings with his camera.
S-21 held over a thousand individuals concurrently, who were often chained and forbidden from speaking. Rations were minimal. Prisoners who violated rules regarding water consumption or speech faced physical assault, lashing, or electric shocks. Crying during these punishments was prohibited. Guards, predominantly teenagers, were not permitted to interact with prisoners.
Under duress, prisoners provided detailed confessions, implicating themselves and others in alleged conspiracies with entities such as the CIA, KGB, or Vietnamese authorities. Following interrogations, prisoners were transported to killing fields and executed with makeshift weapons to conserve ammunition.
Out of approximately 20,000 detainees at S-21, only 12 survived. Among those killed were nearly all foreigners present in the country after May 1975, including two Australians, Ronald Keith Dean and David Lloyd Scott, who were seized, tortured, and murdered after their boat entered Cambodian waters.
Kang Kek Lew, the former chairman of the prison and a mathematics teacher, faced justice in 2012, serving eight years in prison before his death from natural causes.
An estimated one-quarter of Cambodia's population died during the period between 1975 and 1979.