He was not a flashy daredevil pilot who used risky, aggressive tactics (like his brother Lothar, 40 kills) but a cautious, brilliant tactician, who came down on the enemy from above with the sun at his back. He racked up 80 proven kills this way, and if you throw in the likely but unconfirmed, he shot down over 100. (By comparison, the top American Ace was Captain Eddie Rickenbacker, with 26 kills.)
It was a bloody free-for-all in the sky that day; Roy Brown in a Sopwith Camel was part of an RAF squadron, and von Richthofen in his red triplane was leading a full squadron of Germany's best. The Baron was pursuing a Canadian fighter at very low altitude, and Brown flew to the Canadian's rescue. (You know it took some guts to go after a red Fokker triplane...)
A single round of .303 hit von Richthofen in the chest. He managed to land with practically no damage to his airplane, but died just as Allied ground crews rushed up. They reported that the last thing he said was, "Kaput..."
Postscript: The Canadian and Australian forces that retrieved von Richthofen's body gave him a funeral with full military honors, and he was buried at the little cemetery in Amiens. One of the wreaths was inscribed, "To Our Gallant and Worthy Foe." Roy Brown himself said, upon viewing the body, "It brought a lump to my throat. If he had been my dearest friend, I could not have felt greater sorrow." In 1925 the Red Baron was reinterred at a military cemetery in Berlin, then in 1975 was dug up and buried again next to his brother and sister in a family plot in Wiesbaden.
Last word: von Richthofen's red Fokker triplane was quickly dismantled for souvenirs. The engine was given to the Imperial War Museum, where it is still on display, along with the Fokker's machine guns. The joystick can be seen at the Australian War Memorial, in Canberra.
Captain Roy Brown took the seat from the cockpit, which he ultimately donated to the Royal Canadian Military Institute in Toronto. He died of a heart attack on March 9, 1944, age 50, in Stouffville, Ontario. He is buried in Toronto.