Dear Dreamer,
I read your comment and think I may have an idea as to who that guy was. Its good that you remembered that the dream you were having before seeing him was a scary and terrible one. This leads me to believe that the old scary weak man is a symbol of a weight on your shoulders the past problems acculmulating into the form of one man. Overall this shows your power and stubborness. After all since the man is a form of problem you have had it shows how you havent been able to come to terms or to let the problem go. So much so in fact that the poor guy who was once strong and young when he plagued your dreams and mindset, has grown tired of you! Your body and mind has weakened and aged the man rapidly. Im only talking in symbols of course because your mind created the image of the nasty soul/memory that just wouldnt go away. Conjuring up the old man was a sign, something your mind created to make it stick in your memory. Kind of a way to go bonnie message from the brain for kicking this old nasty guy (which is really an old haunting memory or problem) out of your way so you could get some sleep. Heck it even took away the memory of the bad dream too ;)