Casey Affleck in The Assassination of Jesse James by the Coward Robert Ford Kimberley French/Courtesy of Warner Bros.

Any happy coincidences? Any broken bones? Anything that really stood out for you about the whole experience?
I don't think I broke any bones. The whole thing is a happy coincidence in my mind. When somebody says the guy from Chopper is making another movie, and it is this incredible book, and it is this even better screenplay. And guess who's in it? Brad Pitt. You got to go: "Is this a prank?"

How did you hear about the project?
My agent told me that Andrew Dominik is making another movie. And I just said: "I wanna know what that is because I love Chopper." So I went and read the book. When I read the screenplay, it was even better. It was truly one of the better pieces of writing that I have read — ever. Unusual, very rich in detail, heartbreaking, extremely attentive to the facts and wanting to be authentic. I just thought I had to do it. The character spoke to me. Everything about it just seemed so great. And then I suddenly got there and thought: "How am I going to keep up with these guys?" Brad is like he has a hundred hours in his day. He does a million things. He is producing things. He is acting in things. And he still manages to be perfectly prepared and great in every scene. Andrew has really high expectations and high standards, and it was a challenge to try to rise to the occasion and be as good as they were being.

The historical perception of Jesse James and everyone that surrounded him is not the same as the historical fact and the detail that this film brings to the fore. You did a lot of research. What did you unearth that really surprised you about the Jesse James mythology?
Well, what I tried to do — because there really wasn't that much information about Robert Ford — was to know everything I could about Jesse James. Because that is what Robert Ford did. He read all the comic books. He knew every detail of his life. He committed all the dates and places and train robberies to memory. So that is really what I focused on. As well as getting whatever little information I could about Robert Ford. Where he was born, where he lived, what those people sound like. I was talking to people in Virginia and Missouri, trying to blend the two. As far as Jesse James, there has been so much written about him. There have been so many stories, so many movies. Beginning at his death, even beginning before he ever died, he was already a legend about whom untrue things were written. His legend was being created while he was alive. And so, people would read comic books about him. And people in the cities who didn't have any real experience with Jesse James read these books and thought that was what he was really like. Nobody really knew what he was like. He was basically a crook and a murderer and a Confederate soldier. He wasn't a Robin Hood. Or a Che [Guevara]. I think that one of the things that I like about this movie is that it makes both the characters of Robert Ford and Jesse James more three-dimensional: complicated human beings instead of the story-book [version] of a "Robin Hood" Jesse James and traitor-coward Robert Ford.

I heard that you found a photograph of Robert Ford that inspired you and helped you develop the character.
Yeah. I looked for everything I could about him. And actually Andrew gave me this one incredible picture of him that he posed for with the gun that he shot Jesse James with. And there is pride, fear, hesitation, and confusion, all of these things in his face while he is in this very rigid posture. It was really helpful.