One of the more popular interpretations of American Psycho suggests Patrick Bateman never actually killed anyone, and the murderous actions we see played out merely take place in his unhealthy mind.

Was it all in Patrick Bateman's head?

It makes it look like it was all in his head, and as far as I'm concerned, it's not.” Thus, many of the above scenes aren't supposed to be evidence that the murders didn't happen but are supposed to reflect Bateman's deteriorating mental state and the loss of his grip on any semblance of reality.

Who kills Patrick Bateman?

In the non-canon sequel to the movie American Psycho 2, Rachel Newman killed Bateman when she was 12 after he had attacked and killed her babysitter.