American Airlines CRJ-700 collides with helicopter near Reagan National

Pretty good summation of one pilots idea on what happened.

He thinks the helo pilot, when asked if he saw the "RJ" ( regional jet) was looking to his right and saw the jet DEPARTING. When told to go behind, and advised he would, he was behind that departing jet. Unfortunately it was the jet on approach from his left that he didnt see and realize THAT was the "RJ" ATC was referring to.