Actually, this was just an unfortunate situation where the ref was in the line of fire. See, the DB is really making a bee line for the running back and he had tunnel vision, thereby blocking the ref from his line of vision. I hate that he got trucked but it's all part of football.
Oh....and the second guy that it "looked like" finished him off with a bionic elbow from the top rope.....well, he clearly tripped while coming to the ref's aid. Nothing to see here, move along. I just hope neither of the two DB's were injured.