Double Foul - Simultanious Whistle
 

B1 fouls A1 in the act of shooting, the shot is unsuccessful, A2 fouls B2 away from the ball. The whistles by both officials are simultaneous. what should have happened then?:confused:

The situation you have is a simultaneous foul. Play would be resumed by Point of interruption which in this case would be going to the arrow since there is no team control. (Assuming A1 had already released the ball on the shot.)
If A1 was still in possession then I believe Team A would maintain possession for POI.

The POI will be the arrow, in this situation, not simply because there's no team control but also because the try was unsuccessful. If the try would have been successful, the POI would be a throw in for Team B anywhere along the end line (even though when the fouls occurred, there was no team control).