Does anyone know what seeing a shadow person means?

Since moving into our house about 6 months ago, I have seen a young boy on a pretty consistent basis, but never been frightened of him. Last night, my husband kept complaining of seeing smoke in our hallway. Just as he said it, our little girl awoke screaming and inconsolable, which is very unusual for her. After about an hour, we got her calmed down and laid her back in her bed, closing and latching the door like we always do. Just as we were both laying in our bed, we heard the distinct creaking of her bedroom door opening very quickly. I sat up and looked straight down the hallway to see her door wide open, and a large, very dark shadowy figure right next to her door frame. I was literally terrified. Like I said, I have seen things in this house I couldn't explain, but have never felt scared or threatened until now. Does anybody have any idea what this shadowy figure is or what it means? I am very uneasy about this and would really like to better understand what is going on.