Question: Who passed away first, Manfred von Richthofen or Cedric Popkin ?

full_context: Document 1: Richthofen (film): Richthofen (aka Richthofen, The Red Knight of the Air and Richthofen, The Red Ace of Germany) is a 1927 German silent war film directed by Desider Kertesz and Peter Joseph. The film was subsequently re-mastered with sound and music effects and re-released in the United States in 1929. The film stars Georg Burghardt, Sybil Moore and Arne Molander. "Richthofen" was the first film to portray the life of the First World War fighter pilot Manfred von Richthofen.
Document 2: Manfred von Richthofen (general): Karl Ernst Manfred Freiherr von Richthofen (24 May 1855 – 28 November 1939) was a German "General der Kavallerie" (General of the Cavalry) during World War I and recipient of the order Pour le Mérite, known informally as the Blue Max. Richthofen was a great uncle of his more famous namesake Manfred von Richthofen, known as the Red Baron, who was his godson and named after him.
Document 3: Bolko von Richthofen: Bolko von Richthofen (September 13, 1899 – March 18, 1983) was a German archaeologist and a distant relative of the family of Manfred von Richthofen, the "Red Baron". He is sometimes confused with his distant cousin and namesake, Karl Bolko von Richthofen (1903–1971) – the youngest brother of the fighter ace.
Document 4: Erich Rudorffer: Erich Rudorffer (1 November 1917 – 8 April 2016) was a German "Luftwaffe" fighter ace who was one of a handful who served with the "Luftwaffe" through the whole of World War II. He was the 7th most successful fighter pilot in the history of air warfare, with 222 victories claimed. Rudorffer fought in all the major German theaters of war, including the European and Mediterranean Theater of Operations and the Eastern Front. During the war he flew more than 1000 combat missions, engaging in aerial combat over 300 times. Rudorffer was shot down by flak and enemy fighters 16 times and had to take to his parachute nine times. He distinguished himself by shooting down 13 enemy planes in 17 minutes. His 222 aerial victories included 58 heavily armoured Il-2 Sturmovik ground attack aircraft.
Document 5: Snowy Evans: Willy John "Snowy" Evans (  1891 –1925) was a Lewis machine gunner in the Royal Australian Artillery (RAA) during World War I. Unsolved History, produced by Discovery Channel credited him with firing the shot that killed Manfred von Richthofen ("The Red Baron"), near Vaux-sur-Somme, France on 21 April 1918. However, most sources attribute the feat to Sergeant Cedric Popkin of the 24th Machine Gun Company. Other sources have suggested that Gunner Robert Buie, also of the 53rd Battery, fired the fatal shot, but there is now little support for this theory.
Document 6: Lanoe Hawker: Lanoe George Hawker VC, DSO (30 December 1890 – 23 November 1916) was a British First World War flying ace. Having seven credited victories, he was the third pilot to receive the Victoria Cross, the highest decoration for gallantry awarded to British and Commonwealth servicemen. He was killed in a dogfight with the famous German flying ace Manfred von Richthofen ("The Red Baron"), who described him as "the British Boelcke".
Document 7: Manfred von Richthofen: Manfred Albrecht Freiherr von Richthofen (2 May 1892 – 21 April 1918), also known as the "Red Baron", was a fighter pilot with the German Air Force during World War I. He is considered the ace-of-aces of the war, being officially credited with 80 air combat victories.
Document 8: List of victories of Werner Voss: Leutnant Werner Voss (13 April 1897 – 23 September 1917) was a friendly rival of World War I's leading ace, Manfred von Richthofen. Richthofen himself considered Voss as the only pilot with the potential to exceed Richthofen's aerial victory score. When Voss was killed in action, he had scored 44 victories. As can be seen by the list below, his victory roll is well documented.
Document 9: Hermann von Richthofen: Hermann Freiherr von Richthofen, GCVO (born 20 November 1933 in Breslau) is a German diplomat. He is a great nephew of Manfred von Richthofen, the "Red Baron".
Document 10: Cedric Popkin: Cedric Bassett Popkin (Born 20 June 1890, died 26 January 1968) is considered the person most likely to have killed German ace Manfred von Richthofen — also known as the "Red Baron" — on 21 April 1918. Popkin was an anti-aircraft (AA) machine gunner with the First Australian Imperial Force (AIF), during World War I.
Document 11: Max Immelmann: Max Immelmann (21 September 1890 – 18 June 1916) "PLM" was the first German World War I flying ace. He was a pioneer in fighter aviation and is often mistakenly credited with the first aerial victory using a synchronized gun. He was the first aviator to win the "Pour le Mérite", and was awarded it at the same time as Oswald Boelcke. His name has become attached to a common flying tactic, the Immelmann turn, and remains a byword in aviation. He is credited with 15 aerial victories.
Document 12: Manfred von Richthofen (sports official): Manfred von Richthofen (4 February 1934 – 1 May 2014) was a German hockey player and coach. He was also an honorary President of German's national Olympic federation. He was the nephew of World War I German pilot Manfred von Richthofen (the "Red Baron"). His career began during the 1950s. He retired in 2006. Richthofen was born in Berlin, Germany.
Document 13: Erich Hartmann: Erich Alfred Hartmann (19 April 1922 – 20 September 1993), nicknamed "Bubi" ("The Kid") by his German comrades and "The Black Devil" by his Soviet adversaries, was a German fighter pilot during World War II and the most successful fighter ace in the history of aerial warfare. He flew 1,404 combat missions and participated in aerial combat on 825 separate occasions. He claimed, and was credited with, shooting down 352 Allied aircraft—345 Soviet and 7 American—while serving with the "Luftwaffe". During the course of his career, Hartmann was forced to crash-land his fighter 14 times due to damage received from parts of enemy aircraft he had just shot down or mechanical failure. Hartmann was never shot down or forced to land due to enemy fire.
Document 14: Lothar von Richthofen: Lothar Freiherr von Richthofen (born Lothar Siegfried Freiherr von Richthofen; 27 September 1894 – 4 July 1922) was a German First World War fighter ace credited with 40 victories. He was a younger brother of top-scoring ace Manfred von Richthofen (the "Red Baron") and a distant cousin of Luftwaffe Field Marshal Wolfram von Richthofen.
Document 15: The Red Baron (2008 film): The Red Baron (aka Der rote Baron (original title)) is a 2008 German-British biographical action war film written and directed by Nikolai Müllerschön about the World War I fighter pilot Manfred von Richthofen, known as the "Red Baron". The film stars Matthias Schweighöfer, Joseph Fiennes, Til Schweiger and Lena Headey. "The Red Baron" was filmed entirely in English to improve its international commercial viability.
ground_truth: Manfred von Richthofen