Michael has got the story right. Floyd Gibbon's book "the Red Knight of Germany" tells the story. Boelcke attacked a
B.E. 2 several times killing the crew. Boelcke, Richthofen, and the other pilots of Jasta 2 flew along side of the Ghost ship and escorted back to the English lines. The last that the pilots saw of it, was the B.E. flying Westward into a Cloud. Von Richthofen was very moved by the incidence.