Doe posted... In my watch the movie is pretty unambiguous that the murders didn't happen. Paul Allen really did go to London as confirmed by the lawyer, and most of the murders in the movie take place at "Paul Allen's apartment." The London story was discovered by Willem Dafoe, and Dafoe confirmed that Patrick was with his pals the night Paul disappeared.
The sequence from where the ATM tells him to feed it a cat up until he calls his lawyer is flagged from the beginning to not quite be reality. Patrick hallucinates the message from the ATM. Then the police cars explode like an action movie after he fires a couple potshots at it. He even looks at his gun, bewildered, at what just happened.
A particularly critical detail in this sequence is the office buildings. First, Patrick enters a building as though he is fleeing to his office. The clerk spots him so he shoots him, and he shoots the janitor on the way out. Then the next building we see Patrick enter is... clearly the same building. Its layout is identical, and this time Patrick greets the clerk as though he is pulling out a gun but really takes out a pen.
This visual cue of "Patrick says his real, frustrated feelings, then restates the 'appropriate' response" is echoed repeatedly in the movie, and it's no mistake that this scene is presented the way it is. The first building is what happens in Patrick's fantasy, and the following loop is his mundane reality.
It's also noteworthy that the major scenes Patrick has when not with his coworkers are all structured like different genres of fantasy. Patrick records himself with the prostitutes to do his own porno. The chainsaw murder where Allen's apartment is filled with corpses is Patrick starring in a slasher flick. And the police chase is Patrick's action movie.
What is Patrick's recurring catch phrase? "I have to return some video tapes."
Him filming the porno happens after we see a similar porno on his television. The slasher fantasy coincides with him listening to the screams of a slasher flick while doing his morning crutches.
A big part of the film is how similar every body is, and how often people get mixed up. That's why people like the lawyer always calls people by the wrong name. It's very likely he had lunch in london with somebody else he mistook for Paul Allen. He even that Bateman was somebody else in that same conversation.
I thought the building scene was just showing how even the buildings are identical. They copy layouts.