I suffered from sleep paralysis as a child, episodic attacks coupled with night terrors. I know what the "shadow people" look like when you first recover from the paralysis, even though it was until years later that anyone diagnosed what I had. During the attack I wasn't in a half dream/waking state, I wasn't conscious and unable to move, I was entirely functional and under my own control. I stopped looking for real explanations years ago. Thanks though, I realize that the majority of cases for circumstances like these do play back to mental tricks and issues of the brain coming out of a sleeping state and misfiring.