Ask your instructor if the kid in this case dropped his plastic pellet gun after the second shot but was still moving, should he keep shooting until he quit moving.
I could ask, but the answer seems obvious to me. Once the shooting starts, you don’t stop until your training tells you to. I witnessed this first hand in the simulator. The perp, who had started by running at the shooter with a big knife, was already on the ground, looking quite helpless and disabled, but the last of five shots was fired anyway, because he was still moving. It all happens so fast, there is no time to make fine distinctions such as “oh now I realize this is a toy knife (or AK47).” The reflexes were trained. The reflexes did what they were trained to do.
But your question is worth asking, so I’ll call tomorrow and see if he’s available, and try to get you an answer.
BTW, this guy has taught hundreds of police officers in central IL, and he has confirmed one thing frequently mention here on FR, the police he has trained have been notoriously less skilled at shooting and even combat shooting, than hobby or self-defense shooters. They squeeze off 30(?) rounds a year to qualify, and never touch the gun otherwise. So they have no real stress programming. Put them in a serious shooting scenario, and they’re no better off than some total non-shootist dragged in off the street. Comforting, I know.