Perhaps its a shadow self that's not the real person, that normally resides within the person's ego, but in some cases is projected outside the person. This is better understood as a type of ghost perhaps. In ghost sightings, its most often the persons shadow self that is encountered. When a person dies, unless he or she is very highly evolved, that person leaves behind a shadow self from his ego. That shadow self has the memory of that person and believes it is that person, but it is not. Normally the shadow self will disintegrate in time back into the aethers, although it may extend the duration of its existence by feeding on people's negative emotions. This phenomena is different than an actual human personality who may become mired in the astral plane and also encountered as a ghost.