Kind of pointless to pick a single particular time and argue that something would or would not have stopped it without any actual data.
If guns were less prevalent and harder to get would it cause there to be less gun fatalities?
If you are harder on people committing gun crimes would there be less gun fatalities?
If it were illegal to carry large amounts of amnition around with you, would there be less gun fatalities?
If it were illegal to carry around lots of weapons without being in a well-regulated militia, hence where police or other people would see you and go in that person's probably up to no good, would that cause there to be less gun fidelities?
Those statements have a lot more deciding power behind them whether they're right or wrong are you agree or disagree They actually mean something.
If some kid rolls up and does a school shooting do we hold their families responsible? You lived with that guy, prove reasonable doubt that you didn't see it happening and not report it.
But this one time it band camp crap doesn't prove or disprove anything it doesn't say anything about the general working of gun laws on population.