Eeer, you sure about that?
As far as I know, it was an allied soldier (Australian I believe), that shot at his plane while he was doing reconnaissance, and managed to score a point blank shot to the heart.
The story is correct. The RAF credited Captain Roy Brown with the kill (probably wrongly), and the general depiction of events is accurate:
"What happened next remains controversial to this day, but it seems highly probable that Richthofen turned to avoid Brown's attack, and then, instead of climbing out of reach of ground fire and prudently heading for home, remained at low altitude and resumed his pursuit of May, who was still zig-zagging, as he had not noticed that Richthofen had been momentarily distracted. It should be noted that it would have been physically impossible for Richthofen to have done this had he already received the wound from which he died.[3] May and Richthofen's route now took them at low level over the heavily defended Allied front line. Franks and Bennett[3] have suggested that Richthofen had become lost, as the winds that day were blowing the "wrong way", towards the west, and the fight had drifted over to the Allied side. The front was also in a highly fluid state at the time, in contrast to the more common static trench lines earlier in the Great War, and landmarks can be confusing in very low level flight.
Australian Army machine gunners on the ground fired at Richthofen, who eventually crashed near the Australian trenches. Upon viewing Richthofen's body the following day, Brown wrote that "there was a lump in my throat. If he had been my dearest friend, I could not have felt greater sorrow"[citation needed]. His initial combat report was that the fight with Richthofen was "indecisive" - this was altered by his commanding officer to "decisive".[3] Modern historical consensus suggests that Australian anti-aircraft gunner Sergeant Cedric Popkin is the person most likely to have been responsible for the shot that actually downed the Baron.[4][5]
At the time, however, Brown was officially credited with the kill by the RAF, shortly after receiving a Bar to his DSC,[6] at least partly in recognition of this feat."
https://en.wikipedia.org/wiki/Roy_Brown_(RAF_officer)