Thank you! As mentioned in the chapter, this wasn't the first animal he ripped apart. He's done it to several and I doubt all of them were cats. They could have been dogs, squirrels, rats, anything really. It's about what Little Frederick was capable of and how he enjoyed it until the animal stopped screaming, because it was the screaming he looked forward to the most, and how he graduated from animals to humans. Even if it was forced upon him, it opened the doors to it.