Board Thread:Naruto Discussions/@comment-25139119-20140905185119/@comment-1512913-20140906161201

The easiest explanation imo is that Kishi simply forgot to draw Hagoromo and Hamura old and what they were fighting in that panel was the "gedo mazo" that had been extracted from Hagoromo moments ago, thus Hagoromo died shortly after they managed to seal it.