Interesting... I watched it with the sound off, to avoid picking up any preconceptions, and I saw a little boy running right to left under the trees. He disappeared behind a largish tomb, then I saw a vague shadow move up towards a tree branch, then what definitely looked like clothing (jacket? jumper?) swinging downwards. My interpretation was that when the little boy went out of sight, someone swung an item of clothing up towards the tree and then, after a small delay, back down again. Maybe part of it had wrapped over the branch at that point. Hard to tell for sure.
For me, there didn't seem to be anything requiring a supernatural explanation.