There are occasional chapters in Turnabout is Fatal Play from the point of view of the villain. This is from one of those:
It had been so long since he’d felt a true thrill, a new thrill. So very long. It was wonderful that he’d finally found a reason, a necessity greater than the fear of consequences, to move beyond the pleasures of youth, to rekindle the joy of those long ago days, the joy of discovery. This one had been so much better than anything ever before.
The blood splatter, for instance, was really quite nice. Marvelous, really. He had never achieved anything like it with any of the dogs or cats. Of course, they didn’t have nearly so much blood to start with.
The biggest thrill had been watching his subject’s expressions. From surprise to mild irritation to fear to terror to pain to anguish to…what? Resignation? Whatever. The animals never had expressions nearly so good as these.
The only problem had been that it was too fast. That had been necessary, as well, this time. He hadn’t been ready to exercise the care and attention he’d once lavished on the dogs and cats. And this was a subject that had to be quickly eliminated.
He smiled to himself, not only in the pleasure of recollection but in the pleasure of anticipation. There would be no going back to dogs or cats or gerbils or whatever the fuck. He was moving on! Already he had his eye on a new subject.
Again he would have to act quickly, but only in taking custody of her—not in making the kill. This time, he was sure, he could apply all the care and attention to detail that his heart might desire.