Cambodia's Khmer Rouge chief ideologist and "Brother No. 2" Nuon Chea died Sunday at the age of 93, a court spokesman said.
A U.N.-backed court found Nuon Chea guilty of genocide and sentenced him to life in prison last year, almost four decades after the Maoist regime which oversaw the "Killing Fields" was overthrown.
Most of the victims of the 1975-79 regime died of starvation, torture, exhaustion or disease in labor camps or were bludgeoned to death during mass executions.
"We can confirm that defendant Nuon Chea, 93, passed away this evening on 4 Aug., 2019, at Khmer Soviet Friendship hospital," Neth Pheaktra, spokesman at the Extraordinary Chambers in the Courts of Cambodia, said. "Nuon Chea's family has been informed."
Between 1.7 and 2.2 million people, almost a quarter of the population, died during the Khmer Rouge's rule.
Currently, only former President Khieu Samphan and Kaing Guek Eav, also known as Comrade Duch, are serving life sentences after being convicted of genocide and crimes against humanity.