In that example he's done a simple split-screen composite. So we have two shots (both from the exact same camera angle):
Shot 1 - The kid jumping in the air on the left side of the room.
Shot 2 - The kid pointing with his hand on the right side of the room.
Those shots were filmed separately. Then the right half of Shot 1 was removed (or the left half of shot 2, either works), and it was placed on top of shot 2. This gives the illusion of it being a single shot, with the actor appearing twice.
After that, it's simply a matter of pausing Shot 1 at the appropriate point, while letting shot 2 continue.
This is very easy to accomplish in CompositeLab.http://fxhome.com/compositelab/