The balcony he fell from covers the full width of the apartment and is enclosed with a solid metal panel that is at least a metre high -- about the same height as the boy.
There was no furniture on the balcony after the accident, only a mountain bike lying on its side and two pairs of sandals.
There were no trees, canopies or other structures that could have cushioned his fall and the boy fell directly from the balcony to the lawn.
Sounds like a riddle!