Theoretically there's the possibility of friendly AAA shooting him down but I think they would have figured that to be the case very quickly at the scene. Therefore I don't think that is a real possibility.
It still
might have been the case, but wrongly reported afterwards.
A few years ago, I saw a documentation about a similar case where the wreckage of a German nightfighter was discovered and dug out. The remains of the pilot were still aboard, which was a huge surprise as the pilot had gotten a proper and official burial in the family grave. The family had been lied to. (A niece witnessing the burial in 1944 was still alive).
And not only about the grave but also the reason for the death was incorrect. The offical papers stated something like 'shot down in combat by the enemy'. When the plane was uncovered, it was quickly found by specialists that it had been shot down by heavy AA, and research showed there was no enemy plane reported in the airpace at that time at all.
