Sergeant Cole: Captain, what the fuck is up with the phone calls, man?
The Caller: You are going to learn to obey me.
The Caller: The odds are even now, Stu. Isn't that what you wanted? You know where I am and you have a gun. If you have it in you, you can take me down.
Stu: Fuck! They'll kill me before I can get a shot at you.
The Caller: Ah, you're probably right. I wasn't really there anyway. You would've just spoiled some nice lady's curtains.
The Caller: What they don't know, we do to them in our minds, isn't that right?
Stu: You sick fuck.
The Caller: Perfect violation.
Stu: So you'd just whack me for no particular reason?
The Caller: Oh, I've got plenty of reasons. And you keep giving me more.
Stu: I'm on my knees beggin' you not to kill me.
The Caller: Think about it. Why would a guy with a cell phone call a woman everyday from a phone booth?
Pamela McFadden: He said it was quiet.
The Caller: Pam, that's just stupid.
The Caller: You're in this position because you're not telling the truth.
Stu: No, I'm in this fucking position because you have A GUN.
The Caller: You can't understand the pain of betrayal until you've been betrayed.
The Caller: I have no use for you, Stu.
The Caller: That's it, the captain gets a bullet.
The Caller: You'd shoot me if you had the chance, wouldn't you?
Stu: With a big fucking smile on my face.
The Caller: There's the spirit.
The Caller: Get this man a seat on Oprah.
The Caller: Do you see the tourists with their video cameras, hoping the cops will shoot you so they can sell the tape to Goriest Police Shoot-outs?
Answer: The pizza man is intended by the Caller to be a decoy so he can get away. The Caller sends the pizza man to the phone booth so that Stu will identify him later in the apartment, giving the police a convenient answer to the mystery while the real Caller escapes. In fact, at the end of the movie, the Caller comes to visit Stu - obviously he's not the dead pizza delivery man.
Phoenix