Well, there's a theory (based on older belief systems, including OT and other faiths) that our souls are binary (like our brains) that upon death, there is a part that consists of the memories and emotions (but no sentience) of the departed (which the author calls 'soul') and the life force (which would be the 'spirit') and is sentient but has no memories, which goes on to reincarnate. So if this is so, the part that you encountered was a 'soul' and you experienced it's affect. It's just a theory but it explains hauntings and the ideas that most religions have (combined) in a coherent way (IMO).