At the risk of sounding too much "like an attorney" I feel I need to clarify some of the misconceptions about "criminal negligence" or "reckless endangerment" which would be important in any criminal prosecution.
First, there is no requirement for that the criminal actor have any intent to do harm -- in fact crimes like manslaughter exist because there is no intent to do harm.
Second, if the criminal actor's actions are a significant part of the chain which led to the injury, then there would be the causal connection sufficient to support a prosecution. Unless there is the "intervening, superceding event" which "breaks the chain of causality" (you gotta love those phrases!) the causal connection will be sufficient to create liability.
Some of you may remember the movie with Jodie Foster about the rape of a drunk woman in a bar (it is a real story). The onlookers were charged with aiding and abetting the rape (in effect, I can't remember the actual charges) and were eventually convicted. Their "crime?" They yelled encouragement to the guys who did the actual rape.
I'm sure you also have all heard about bar tenders who have been held liable (civilly not criminal as far as I can recall) when they let drunks drive and kill people. They didn't encourage the driving, but they were in a position of "authority" that gave them a duty to prevent it if they could.
And, lastly, there are the groups of drunks who actually DO play Russian Roulette -- and the survivors can, and have, been charged with manslaughter for letting the other idiot pull the trigger.
For some pretty good reasons, society has declared that people should not be permitted to encourage deathly activity and then not be held responsible for the resulting death.
Here, EVERYONE knew, or should have known, this was a reckless activity with a significant chance of a death occurring. Given the facts as we assume them to be, the one with the most culpability was the "instructor" because he had the special knowledge (not to mention the leadership role). It shouldn't be a huge leap to find this case to be a classic Man 2 or even Man 1 (I really think it was recklessness, not negligence and thus the higher standard/culpability).
Me, I'm glad Society has these rules to counter the toxic effects of testosterone.