>I believe there's no explanation that he could give and be happy to be known for. But if you read the book you get a sense of motive. It was a compulsion, something which gave him a sense of control and at times pleasure or satisfaction or power. And the consequences of his habit (the death of innocent people) didn't really weigh on him negatively, so there was no reason (in his mind) to stop.

Author about killer's motive