Block or Charge?

[tmp44]

IM Championship Game on Thursday Night. I am C, table side. Deep 3-point FG by A1 hits the back of the rim and leads to the rebound coming all the way out to approximately the 3-point line. B1 jumps high to get the rebound, and in the process of getting the rebound, begins to turn in the air so that he can begin a fast break going the other way. As he is getting the rebound, A2 sets himself to take a charge as B1 comes down. B1 turns while in the air, has his first foot hit the ground, and then the crash occurs. I immediately came with a block, and explained to the defender that he never allowed the rebounder the opportunity to fully come down on the court. I know this may be one of those "had to be there" plays, but what does everyone think?