In the old days, it was quite common practice for someone to take a bag full of puppies, fill it with rocks and sink it. Or, at least we all heard that there were people out there who did that. And in the country, folk get strays dumped on them all the time. Who hasn't heard of a farmer shooting some strays to keep them away from his lifestock. I think the difference here is just the callous way she casually throws the puppies in the water, almost as if she's doing a quarterback drill and grabbing some footballs to throw through a tire. Would we react the same if she loaded them all in a bag of rocks and sunk them into the creek?