From "The Red Baron's Last Flight, a Mystery Investigated" by Norman Franks and Alan Bennett.
Four claims were submitted against Richthofen. The first was by two RE8s from 3 AFC. Lt. T.L. Simpson and Lt. E.C. Banks (in A3661) and Lt. S.G. Garrett and Lt. A.V. Barrow were attacked by two Fokker DrI triplanes while on recpn missions. The first, an all-red triplane, spun down and didn't return after a protracted battled. The second triplane received hits and also disengaged. After reading that Richthofen had come down near where they had been flying, the 3 AFC pilots put in a claim.
The second claim was by Capt. A.
Roy Brown DSC, in the 209 RAF. As mentioned previously, he was attempting to save Lt.
Wop May (Canadian, I believe) who was being chased by Richthofen. Brown is credited with the kill officially.
The third claim came from a pair of ground gunners. Gunner Robert Buie and Gunner William James Evans, of the 53rd Battery, also claimed to have shot down Richthoven.
The final claim, which was made a little later than the others, was by Sgt. Cedric Popkin of the 24th Machine Gun Company.
Franks and Bennett conclude that Popkin was the man responsible for getting Richthofen. The book is an excellent read and I recommend it.
Droops