Why?

I'm always surprised when I see a child, usually a boy, be abusive to an animal. This afternoon I heard children playing around the pond. I got up to snap a few pictures of children enjoying nature only to be shocked when the older boy picked up a stone and threw it at a duck. The stone hit the duck. The boy was excited and was shouting to his brother "did you see that? I really hit that duck" and then I began to scream.

My scream must have been loud enough to shock the little boy because he fell on his butt and looked around. His little sister saw me and was shouting across the pond, "what is your name". I stared that little boy in the eye and told him you never throw stones at a living thing. He began to cry and said he was sorry and ran off to the comfort of his Dad who was standing by some cars in an entirely different apartment complex over.

Why do children do this? I remember being in second grade and Rex T found some baby bunnies in a rabbit hole. Before recess was over he and another boy had tossed every baby bunny into the air and laughed as they hit the ground. I ran to the teacher on recess duty as the first bunny was flung into the air and by the time she arrived at the rabbit hole, all the bunnies were dead. Why, why, why?

Does it make the kids feel powerful? Are the children abused at home so they take their frustrations out on something smaller? Or are they just bad kids?