Tap situation

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Gentlemen and women: Team A shoots from just inside the top of the key and catches the back iron at a hard angle resulting in a high, reasonably long rebound (just inside the free throw line, center of the lane). Both A1 and B1 are there awaiting the rebound (you know the look--semi-crouch; heads cocked upwards; eyes glued on the ball) when A2 runs up the lane (from the approx. area the shot was taken), places his right hand on the left shoulder of A1, and skies to tap the ball with his left hand towards the basket for what by all appearances will be a successful tap/try.

Two questions:
1) is there anything to be called in this scenario?
2) if so, whose primary jurisdiction?

Feel free to finish it with whatever appropriate insight can be made.