Shriekers are classed as apex predators in the Valley, meaning you're technically not supposed to kill them if you can possibly avoid it. Obviously a life and death situation such as this one grants you an exception.
Poachers, of course, are a thing, and many have put forth the excuse that they were just defending themselves and well, since it's already dead, shouldn't let it go to waste, right?
Which then gives rise to the discipline of hunting forensics, where investigators attempt to determine whether the wounds on the creature are consistent with self-defense (e.g., slashing wounds on the front), or not (e.g., a projectile through the back of the skull).
My Valley of the Silk Sky short story "Extraction," featured in the Monster Journey anthology, deals more specifically with protection of apex predators, so check that out if you're keen.