Question: What country was featured in the Killing Fields?

Context paragraphs:
Sri Lanka's Killing Fields: War Crimes Unpunished: Sri Lanka's Killing Fields: War Crimes Unpunished was an investigatory documentary about the final weeks of the Sri Lankan Civil War broadcast by the British TV station Channel 4 on 14 March 2012.  It was a sequel to the award-winning "Sri Lanka's Killing Fields" which was broadcast by Channel 4 in June 2011.  Made by film maker Callum Macrae, this documentary focused on four specific cases and investigated who was responsible for them.  Using amateur video from the conflict zone filmed by civilians and Sri Lankan soldiers, photographs and statements by civilians, soldiers and United Nations workers, the documentary traced ultimate responsibility for the cases to Sri Lanka's political and military leaders.  The documentary was made by ITN Productions and presented by Jon Snow, the main anchor on Channel 4 News.  The Sri Lankan government has denied all the allegations in the documentary.

Chankiri Tree: A Chankiri Tree or Killing Tree was a tree in the Cambodian Killing Fields against which children and infants were smashed because their parents were accused of crimes against the Khmer Rouge.  It was so the children "wouldn't grow up and take revenge for their parents' deaths".  Some of the soldiers laughed as they beat the children against the trees.  Not to laugh could have indicated sympathy, making oneself a target.

Killing vector field: In mathematics, a Killing vector field (often just Killing field)), named after Wilhelm Killing, is a vector field on a Riemannian manifold (or pseudo-Riemannian manifold) that preserves the metric.  Killing fields are the infinitesimal generators of isometries; that is, flows generated by Killing fields are continuous isometries of the manifold.  More simply, the flow generates a symmetry, in the sense that moving each point on an object the same distance in the direction of the Killing vector will not distort distances on the object.

Bangla College killing field: The Bangla College killing field is located in the Mirpur area of Dhaka, Bangladesh.  In 1971, during the Bangladesh Liberation War, the Pakistani army killed 3 million Bangladeshis with the help of some local collaborators.  It has been claimed to be the largest genocide after World War II.  Bangladesh officially became independent on 16 December 1971, but the neighborhood of Mirpur was liberated from Pakistan Army and local Bihari people on 31 January 1972, 45 days after the declaration of independence was signed.  Mirpur was largely inhabited by Biharis who were against the secession movement, so genocide took place on a large scale.  Mirpur was the last battlefield of the war.  Bangla College is one of the largest killing fields in Bangladesh.

Roland Joffé: Roland Joffé (born 17 November 1945) is an English-French film director who is known for the Oscar-winning movies "The Killing Fields" and "The Mission".  He began his career in television.  His early television credits included episodes of "Coronation Street" and an adaptation of "The Stars Look Down" for Granada.  He gained a reputation for hard-hitting political stories with the series "Bill Brand" and factual dramas for "Play for Today".

Sri Lanka's Killing Fields: Sri Lanka's Killing Fields was an investigatory documentary about the final weeks of the Sri Lankan Civil War broadcast by the British TV station Channel 4 on 14 June 2011.  Described as one of the most graphic documentaries in British TV history, the documentary featured amateur video from the conflict zone filmed by civilians and Sri Lankan soldiers which depicted "horrific war crimes".  The video filmed by civilians included harrowing scenes during and after intense shelling of civilian targets, including hospitals, by the Sri Lankan military.  The "trophy video" filmed by Sri Lankan soldiers showed disturbing scenes of blindfolded victims being executed and dead bodies of naked women being dragged onto trucks by soldiers as they made lewd remarks about the victims.  The documentary also included interviews with civilians who managed to survive the conflict, United Nations staff based in Sri Lanka during the conflict, human rights organisations and an international law expert.  The documentary was made by ITN Productions and presented by Jon Snow, the main anchor on Channel 4 News.

Killing field: A killing field, in military science, is an area in front of a defensive position that the enemy must cross during an assault and is specifically intended to allow the defending troops to incapacitate a large number of the enemy.  Defensive emplacements such as anti-tank obstacles, barbed wire and minefields are often used to funnel the enemy into these killing fields.  The fields are generally cleared of most cover so that attackers are exposed when being fired upon.  Some methods of destroying the assault capabilities of attacking forces include machine guns, artillery and mortars; often with interlocking fields of fire.  Such a term may be used to describe the approaches to an "ideal" defensive fortification.  An example of a killing field would be the exposed beaches in front of the seawall at Normandy.

The Killing Fields (film): The Killing Fields is a 1984 British biographical drama film about the Khmer Rouge regime in Cambodia, which is based on the experiences of two journalists: Cambodian Dith Pran and American Sydney Schanberg.  It was directed by Roland Joffé and produced by David Puttnam for his company Goldcrest Films.  Sam Waterston stars as Schanberg, Haing S. Ngor as Pran, Julian Sands as Jon Swain, and John Malkovich as Al Rockoff.  The adaptation for the screen was written by Bruce Robinson; the musical score was written by Mike Oldfield and orchestrated by David Bedford.

Texas Killing Fields: Texas Killing Fields (also known as The Fields) is a 2011 American crime film directed by Ami Canaan Mann, starring Sam Worthington, Jeffrey Dean Morgan, Jessica Chastain and Chloë Grace Moretz.  It competed in the 68th Venice International Film Festival in September.

Lies Agreed Upon: Lies Agreed Upon is a documentary produced by Sri Lanka Ministry of Defence in response to a documentary aired by Channel 4, named "Sri Lanka's Killing Fields", about the final weeks of the Sri Lankan Civil War.  The documentary gives the Sri Lanka Ministry of Defence response to war crimes accusations and rebuts points made by the producers of the Channel 4 documentary, who presented it as "a forensic investigation into the final weeks of the quarter-century-long civil war between the government of Sri Lanka and the secessionist rebels, the Tamil Tigers."  "Lies Agreed Upon" was first aired at an official function held at Hilton Hotel, Colombo on 1 August 2011, one and half months after the broadcasting of "Sri Lanka's Killing Fields".  Ministry of Defence released another report named "Humanitarian Operation – Factual Analysis : July 2006 – May 2009" on the same day.

Supporting paragraphs: Roland Joffé The Killing Fields (film)
Answer: Cambodia