Richthofen was killed by a single .303 bullet which was fired from the ground. Richthofen died following an extremely serious and inevitably fatal chest wound from that single bullet, penetrating from the right armpit and resurfacing next to the left nipple.
It is generally agreed that Sergeant Cedric Popkin was the person most likely to have killed Richthofen. Popkin was an anti-aircraft machine gunner with the Australian 24th Machine Gun Company, and he was using a Vickers machine gun. He fired at Richthofen's aircraft on two occasions: first as the Baron was heading straight at his position, and then at long range from the right. Given the nature of Richthofen's wounds, Popkin was in a position to fire the fatal shot when the pilot passed him for a second time, on the right.
