May I suggest a couple of things further.

Before we assume that BB fired "without knowing where her bullet would end up" , let's bear in mind that this is far from true in absolute terms. She was firing at a downward angle at relatively short range.... and a tectonic plate is usually regarded as a pretty reasonable backstop. Even against .300 Magnums.

Secondly, "negligence" is being used in this context without fully considering whether it is justified. If we accept the normal definition that it is the lack of "due" or "reasonable" care, then one has to argue that the "normal" care to be taken when shooting at an aggressive and wounded member of a known dangerous species..... is to trot up and check the grass beneath it.

This best parallel in this case is not a negligent discharge ( which is unintended), nor is it the person who shoots at movement in the bush under the impression that it is a deer. The most appropriate similar case is that of a policeman who fires in order to provent a crime against life, and unintentionally injures someone on the other side of the thin wall.

It is unfortunate and regrettable, but it is not negligence because the shooter could not be reasonably expected to ensure absolute safety under the constraints that existed at the time.

Let us not be so foolish as to believe that perfect safety is achievable, or that it is *reasonable* that we plan for every possible contingency at all times. Aeroplanes crash, yet how many of us here think that it would be sensible or reasonable to carry a parachute when flying on RPT?

"Let he who is without sin, cast the first stone....."