Just tested IWT on beta as a hunter.

If you're not in combat and facing away from a mob, it won't do anything.

If in combat, facing away, and under say 10 feet from the mob, the hunter will turn to face the mob and shoot. If the mob is on top of him, he will turn and point blank shoot, no melee for the hunter. Farther than the estimated 10 feet distance, nothing.

If you are facing the mob, in combat, but out of range, the hunter will run towards the mob just enough to get in shooting range, and shoot.