You could infer that the accidental shooter had non-existent trigger-finger training. (and several other deficiencies as well)
That's the single biggest thing I see newbies doing wrong - finger on the trigger at the wrong time. Because your finger goes there so naturally.....
Last training of a newbie I had her old the lower to my disassembled Glock with finger off the trigger to give it time to burn into her muscle memory that that is how you hold a gun.
We'll see if that helped next time we go shooting.