I had my daughter at a playground and I wanted her to go on the swings with me. She wanted to do the slides first. I looked over at the swings (which were still before this) and noticed the one closest to me was swinging. It even looks like someone is sitting in it the way the seat is bent. There was zero wind and not a single person around. We were alone at the playground. The swing was moving like that for over 10 minutes. When I looked back later it was not swinging but had a side to side movement as if someone got off of it. I am going back to that neighborhood today so I'm going to check it out.