Man in gray seen in my bedroom when I was a child of around 4 years old.

Not sure of the date.  I was about 4 years old and in my bed in my own room.  It was if I remember right late spring.  I was asleep in my bed.  As I opened my eyes I saw a man standing in the corner of my room.  On each wall there was a window but he was either in the window on the left wall or in the corner between the two windows. 
At first I was peaceful... just looking at him.  Then I realized that I did not know him.  I yelled for my mother, "There is a man in my room!"  She came into my room, and stopped to light her ever present cigarette...  I remember the red glow on the point of the cigarette.  She said, "Where?" and I said, "There in the corner."  She went and stood in the corner and asked me, "Where is he now?"  I said, "He is gone."  
She stepped out of the corner, and I said, "There he is!"  She asked me if he had come in through the window…  I said no…  She asked me if two bodies could stand in the same place at once?  I said no.  She asked me, where he was now?  I said he is in the corner!!!  She stepped into the corner, and again I could not see him.  Then feeling sure that there was no one there.... she said, "There is no one here!  I am going back to bed."  And she left the room.  I was frightened but have no further memory.  The man was wearing some kind of a uniform... it looked military... grayish.
Had on sunglasses... or large-ish eyes....  He was as tall as my mother or a bit taller... around five six ft.  I never saw him again.
When my mother was there, I was completely awake and yet I could still see him.  She could not.
Witness indicates that the date of the sighting is approximate.  PD