There is an even more likely possibility. For some, a fire fight is pure terror and panic. It would not be beyond reason, a panic'd troop standing there, after firing his first round and reloading. Then, in the chaos and panic of the fire fight, loading again, even if he hadn't fired another round.
I was involved in two incidents during fire fights. In one, at the scene of an armed robbery, I and my partner cornered the thieves and a gun fight ensued. After the gun fight was over, I heard clicking from my right. My partner was standing there, still snapping on empty chambers. Had never reloaded. In the second, my partner had found cover. After the fight was over, I found him standing in a small alcove, gun in hand, gun raised in front of him. Never fired a round. Totally panicked. I never rode with either of those two again. They also didn't last long in the police business.
Coffinmaker