Where is the proof that it was done on purpose? Perhaps it was a wild shot at something else that just happened to land where it did. If this is cruel, then any time an animal is hit by a car on the road, it should be considered cruel and a bounty should be posted for the "responsible persons."
Guilty until proven innocent, that's not the way it is suppose to be. Unfortunate, but not necessarily cruel, until it is proven.
On another note, kangaroos to Aus. is like deer to the US. They are everywhere. Are kangaroos hunted like deer is here? Without hunting, the deer would be wildly out of control here in Pennsylvania.