Well, while he obviously failed in accomplishing it, doing a simulation without live ammo should have fit the bill. To be honest, without more detail, I am not sure how much stock I would put in the excessive force allegation, yet. They are not uncommon.
This feels like jackassery on so many levels. The revolver...why? Semi-auto sims work requires a replacement slide assembly which would have made it impossible to shoot live ammo. The average police arms room has numerous extra duty weapons. In 20/20 hindsight, the desire to have a slice of criminal life gun (revolver) vs. the same weapon the department carries seems not worth the risk, though as I said that is in hindsight.