No one is above the rules
One of the students involved in this went up and took the blank gun … from the instructor’s [emphasis mine] waistband and placed that against the instructor’s back and fired
Not the student’s fault. No one is supposed to have weapons capable of causing injury at such an event.
Either the school’s training protocols are incorrect or the instructor didn’t follow them. Either way, this incident is on the cadre not the student. This is a Serious Mistake on the trainers’ side. There are reasons we have rules about how to conduct Force on Force. This is an example of why. Fortunately, it appears the injury wasn’t serious but the incident is an example of how Negative Outcomes occur.
Guns are deadly weapons. We can never relax our vigilance around them. Thinking that anyone is exempt from the rules is “cruisin’ for a bruisin’.