Seems like it was the combination of them both that created the pure evil that they became. What is really trippy about it is you wonder if anyone would have gotten killed if these 2 guys didn't hook up.they were cousins, and the one was such a fuck-up from NY state and went out to crash with his older cousin in LA.
Also I read a book on the Hillside Stranglers called 2 of a Kind or Just the 2 of Us or something like that, and it was really crazy.