Revisiting the Little Prince
Just posting an almost obvious theory connecting what we know from 316 and what happened in The Little Prince.
In The Little Prince, we see Sawyer and co. taking a boat and paddles and paddling around the island, before they start getting shot at. We have since wondered who was shooting them. Right before the paddle, they see an Ajira Airways water bottle, the airline that the O6 came back to the island on.
So one theory is that it was the O6 who were shooting at them, as they can have guns via Jin, who we see at the end of 316 pointing at them. Perhaps he has more in the van. However, I do not remember seeing Jack or Hurley or Kate having a water bottle on them.
This is why it could also be some 316 survivors from the tail section of the plane shooting. Either way, it safe to say that it has been narrowed down to who was shooting at them.

The lady escorting Sayid and the guy with his seatbelt undone got way too much face time to be extras.
Yes, I was thinking it could be the two of them, Sayid, and maybe Sun as well.