The Polar Express Movie Question?

In the Movie "Polar Express" there is that hobo dude sitting on top of the train and he asks the kid, "Do you believe in ghosts?" and so at that point I thought he was a ghost since he disappeared and reappeared in and out of the movie. Then the man operating the train was telling the kids how he almost fell off the train once and a person helped him up then disappeared. Then the little girl said, "Was it an Angel?" My mom and I had an arguement, so help me settle it. Was the hobo guy a ghost or an angel? Please explain your answer.