Free Throw Violation

[Mike O]

I had a situation the other night where A1 was shooting the first shot of two shot free throw. I handed the ball to A1 in preparation of the free throw. A2 then moves from his lane position to the backcourt. My question is do you blow the shot dead at this point of allow the shooter to attempt the free throw? What would happen if B1 then violates after the shot? Does A1 get to attempt the second shot? My partner blew the attempt dead and gave the ball to team B.