Brown had an exceptional record as a fighter pilot and as an instructor. He had not lost a single pilot in his squadron. As May was still a novice, his training included patrols that brought a few encounters with the enemy. On 21 April, May flew with the squadron over the lines and encountered Lieutenant Wolfram von Richthofen and his cousin Rittmeister Manfred von Richthofen, known as the Red Baron, and his Jasta 11 squadron.

May had been instructed not to engage the enemy but to fly above the fray: watching and learning. He encountered a German aircraft that had been instructed to do the same. The plane appeared to be an easy target, so he engaged the enemy in a dogfight. It was the cousin of Richthofen who piloted the aircraft he was attacking. May missed his target, and suddenly found himself in the middle of an attack with aircraft coming in and firing at him from all directions. He went into a steep turn and fired at the German, missing his target just before both of his guns jammed.

To get out of trouble, May spun out toward the west, but quickly realized he had a German triplane (piloted by the Red Baron) behind him, which shot his aircraft in the tail. Roy Brown had seen the events unfold, and was now behind the Red Baron as May dropped down until he was flying just above the battlefield, making his way back to his side of the line. Roy Brown fired at the Red Baron as they flew over gunners on the ground, who also fired at the red triplane, which crashed into a hill. The Red Baron died from a gunshot wound.

Roy Brown was awarded a bar to his Distinguished Service Cross for the victory over the Red Baron.