Please answer the following question: Generate a question that has the following answer: 1999 for the following movie plot: An estimated 1.7 million Cambodians died during the rule of the Khmer Rouge, a radical communist movement led by Pol Pot. Among the victims were Thet Sambath's mother, father and brother. He says he did not understand why the Khmer Rouge unleashed such violence on their compatriots. In 1999, he decided to seek confessions and explanations from former Khmer Rouge officials at all levels. None had previously admitted any killings.[1] In 2001, he met Nuon Chea, Pol Pot's deputy, also known as Brother Number Two. Nuon Chea was then living as a private citizen in Prum, a small town on the Thai-Cambodian border. Sambath visited Nuon Chea most weekends for around three years.[2] During that time, Nuon Chea was willing to talk about all phases of his political career except the three-and-a-half years of the Khmer Rouge regime. He had previously been interviewed by Western and Japanese journalists but had always denied responsibility for killing anyone in the Cambodian genocide. In 2004, Nuon Chea made his first admission to Sambath concerning decisions to kill that he made with Pol Pot.[3] Sambath continued to interview Nuon Chea on his role in the Killing Fields for three more years. During that time the United Nations-backed Extraordinary Chambers in the Courts of Cambodia (ECCC) was constituted to investigate the alleged crimes of Democratic Kampuchea. Sambath interviewed Nuon Chea until September 2007 when the latter was arrested and charged with war crimes and crimes against humanity by the ECCC. During the same period, Sambath also built up a network of less senior former Khmer Rouge officials and cadres who were prepared to acknowledge and detail their role in the Killing Fields.[4] The film focuses on two Khmer Rouge perpetrators in the northwest of Cambodia. Khoun and Suon take Sambath to the scene of their massacres and introduce him to their superior officer, a woman known as Sister 'Em'. They give graphic accounts of the massacres they perpetrated. They also give voice to their own feelings of...
Answer:
What year does Thet Sambath seek confessions and explanations?