I've seen ghosts before... and I heard them. But I have some doubts about how they actually turn into ghosts.
Some people think that with the right time and satus of the area around them, history will repeat itself, like a movie, or a flashback but the people in the dream or flashback will not be aware of what they're doing or the area around them... Like they'll just be there... It's creepy when you think about it.