Free throw violation

[rbruno]

Think we might have messed this up.
Player A-1 is at the line for the first of a one and one. He has the ball and is ready to shoot when one of the players notices that B-1 is not occupying a lane space adjacent to the basket and is switched with A-2 who is in that space.
Before the shot A-2 and B-1 realize that they are in the wrong spaces and change positions. The trail official calls a free throw violation on A-1 and awards the ball to Team B under the hoop.
Should this have been a double violation with the possesion arrow determining who got the ball?