So, I've had 2 shadow person encounters involving other people.
Of course, you have no reason to believe me, and I can offer no proof, however I sincerely swear that this actually happened.
Both incidents took place before I had ever seen mention of shadow people online.
I was active on usenet alt.conspiracy, alt.alien.visitors, and so on. and never saw a thing about them, so imagine my terror later in life when I saw drawings of these things online.
When I was young, my sister and I shared a room. My bed was on one side, hers on the other, and we had a closet in the middle on the far side of the room which was always open.
From my bed, I could see the closet door but not the inside. From hers, she could see inside.
When I was maybe 8 years old, I woke up with what I now know was probably sleep paralysis. I saw a black shadowy hand and arm slowly reaching out from the closet.
Freaked the hell out of me. For years I chalked it up to my imagination.
Around the year 2000, I was talking to my sister about our old house, and she asked if I ever saw the man in the closet.
I had never told her about what I had seen, but she described seeing a textbook shadow person, complete with hat, standing in the closet and slowly reaching an arm out.
The other incident happened when I was in highschool, in a different house.
Friends and I were sitting in the livingroom, downstairs, watching Beavis & Butthead on MTV at around 1:00 a.m., having a good time, laughing, when I got an overwhelming sensation of fear, that I had to get out now.
This is very unusual and I can't remember ever feeling this sort of fear outside of a sleep paralysis situation, which is also very rare for me. I stood up from the couch and ran outside.
After I calmed down, I went back inside and was fine but shook.
The next day, my mom was driving us somewhere, and she asked if anything odd had happened the night before. She described waking up around 1:00 a.m., seeing a shadow in her room, and trying to figure out what was casting it, a tree from outside, or whatever.
As she focused on the shadow, it seemed to get more solid, and she realized it had the appearance of a man in a long coat and black fedora hat.
As it became fully real and she was about to flip on the light, it collapsed in to the floor Obi-Wan Kenobi style as though the person inside the close had vanished.
The spot in her room where it was standing was directly over the spot where I had been sitting.