Black Shadow In Middle Of Lit Room?

A few months back I was having a conversation with my father about my grandma in my parents room. All of the lights were on, and the three dogs were lounging around the bed. Mid conversation, I saw a black semi-transparent figure about 5'10" in height walk by and trace the perimeter of the bed to the other side. It lasted about 2 solid seconds, and at the very same time I saw it, my father looked up to watch it and my dog who is fairly blind from diabetes, went after it barking and snarling. It was located in the middle of the room, and appeared no different than a person would. Definitely the clearest unexplained sighting I have ever experienced. A shadow would have appeared on a wall or on the floor. By far the most interesting thing about this sighting is that it was clear as anything and in a very well lit room.

I looked at my father immediately after it had dissapeared and said "what was that"? He said "I don't know and I don't want to talk about it". We talk about it all the time, but it definitely freaked him out. Wish my mom wasn't reading her book in the corner, because she would have seen it heading right for her where the dog dodged.

I am trying to get a little insight into what I saw. My friend offers religious explanations and beleives it's a demon, but I don't know. I am open minded and definitely a bit intrigued. I have had some very weird occurences take place in my lifetime, but this is by far the most intersting.

If anybody has any advice, opinions, similar experiences to what I saw, I would be interested in seeing what you have to say.