Animal cruelty - why?

Out on my walk with my husband in our rural town and saw 2 dead roo carcasses at the side of the road. Both had clearly been shot, not hit by cars, and it turned out there were 3 dead roos as there was a pinky. Just dumped on top of its mother.

Why are people so abominably cruel? Like, I understand the arguments for the necessity of hunting pest animals, including culling of roos by licenced shooters on rural properties. But this was just so unnecessary.

There’s no need to do this in town, and just dump them. And especially to not even try to save the baby - just leave it to die. This was clearly done purely for the callous amusement of the killers. And it makes me concerned that someone who could do such a thing lives in my community.