If you watch the video very closely, you can see that the flight deck is elevated from the stern deck area (watch the helo's shadow closely to see this). When the helo went over on the left of the flight deck, it fell off of the flight deck and landed on the ship below. The flames originate from below and graze the side of the flight deck.
For all to have survived with only minor injuries speaks volumes about the way Sikorsky builds their helos.