Silhouett of a person

My cousin and I were in the kitchen talking and all of a sudden there was a silhouett of a person on the back porch at the kitchen door. it was so real like that I was going to open the door to see who it was, but as quick as it was there, it disappeared just as quick. I looked on the porch to see if I seen anyone and cousin looked out kitchen window to see if she could see anyone and neither one of us seen anyone.