Photo of Kaing Guek Eav at his 2009 trial 

Khmer Rouge’s chief jailer, Kaing Guek Eav, also known as Duch, has died after admitting to overseeing torture and killings as many as 16,000 Cambodians whilst running the regime’s most notorious prison.

Duch died in the Cambodian Soviet Friendship Hospital at the age of 77. He was serving a life prison term for war crimes and crimes against humanity. He was the first senior Khmer Rouge figure to face the U.N. backed tribunal in 2009 for massacres which killed approximately 1.7 million people, roughly a quarter of Cambodia’s population at the time, during the late 1970s.

The Khmer Rouge ruled Cambodia from 1975-79 and has been accused of genocide due to mass executions, starvation and lack of medical care provided by the regime. In 2004, the UN and the then Cambodian government established a tribunal to investigate these atrocities.

The New York Times reports that since Dutch’s trial, two high-ranking Khmer Rouge leaders have been convicted and further two others have died before their trials could be concluded. Nuon Chea, the regime’s No.2 leader, died during his appeals process.

The New York Times further reports that the former head of state Khieu Samphan, will “almost certainly” be the last one to face trial, due to the Cambodian government’s opposition to more prosecutions.

Read more from the New York Times.