We still don't know exactly how the gun was or was not 'secured,' do we?
I'm very curious about this, having recently shopped for gun lock boxes and purchased two of them-- reading the negative reviews was really informative. For example, some-- with keys that are bilaterally symmetrical-- can be opened, literally, with a paper clip. There are six-year-olds who could do this. A six-year-old might also be able to remember the combination of one of those stupid little zinc locks, if he saw mum or dud open the safe. Some fingerprint sensors do not work well-- I've seen reviews that said, "I quickly discovered that any finger would open the safe, whether it had been programmed or not." Most can be pried open with screwdrivers, though some would require more strength than a young child would have.
My impression is that most lock boxes are pretty bad. The larger one I got seems pretty decent, though the fingerprint sensor is wonky-- I sometimes I have to use the combination. I'm going to test it with the 'wrong' finger. The smaller safe, though it has a cylindrical key, is really not great. I think it has a reasonable chance of deterring a smash-and-grab thief, or it would be fine for the trunk of a car with an alarm (if I can find a decent anchor point for the cable) if I am nearby.
OTOH, "secured" could mean "in a locked briefcase" or the trunk of a car or something, which would be a bit different. It's negligent either way, but it would be useful to know how negligent-- and if the answer turns out to be, "the kid broke into a lockbox," I'd like to know how the security was defeated.
“Freedom is something that dies unless it's used.”
― Hunter S. Thompson