Phnom Penh was emptied of people by the Khmer Rouge in April 1975. While most people lived and died in rural parts of Cambodia this Phnom Penh high school this lady went to was turned into a prison and place of torture. About sixteen thousand people died there.
Today it is a museum, I’ve been a few times. You can walk through the building and see photos of the people they killed, torture instruments, cells where they kept people, some made from wood, some brick. Another part shows a big room where the prisoners where kept, not in cells, but chained together on the floor.