>> he said he found the noise annoying. >> only looks at the events from his own perspective. this is a script designed to please him. because remember, it was almost like these people weren't real. they were just actors, and they didn't matter. what mattered was his enjoyment. the kids screaming was taking away from his enjoying all of this stuff. how can he get aroused with the kids screaming? >> he completely dehumanizes the kids? >> yes. serial killers are very good at that. that makes it possible for them to kill. >> it was something i had to do. once i started with mr. otero i knew i had to do all four of them. it was like an execution. once you start it, if there's witnesses, you had to do it all the way around. >> for someone who seemed so callous, you might assume rader was always a coolly efficient killer. but the way he tells it, rader