The biopic “Black Mass” starring Johnny Depp as notorious Boston gangster and FBI informant James “Whitey” Bulger is in theaters September 18 with Joel Edgerton costarring as FBI agent John Connolly. Edgerton spoke with FOX411 about the pressures of playing a real person, his reaction when he first saw Depp transformed physically into the character, plus how the role stands out for him considering he’s already getting plenty of early awards season buzz.

FOX411: The pressures of playing a real person especially in a story like this where people know some… but you sort of have to give the rest.
Joel Edgerton: Yeah, you tell a true story and it’s like what is the truth? Who knows the truth? Do we, even any of the real people involved in the story, they know part of the truth and it’s everybody’s sort of separate versions of the truth cobbled together create a version of a story and now here we are a bunch of directors, actors, producers, writers all going ok well now we’re going to pretend like we know the truth. I think you need to sort of acknowledge that it’s just our version of the story.

FOX411: How much were you given and how much did you have to sort of fill in the blanks?
Edgerton: The story was there, the dialogue was all there, and the events were there, and the book “Black Mass” was there which fills in more detail. In many ways my job was just to really sort of examine the motivations of the guy. Because it’s such an odd relationship he had with Jimmy Bulger. It’s such an odd set of circumstances that led to it and it’s such an odd series of events that came after their connection and this sort of bond that they made for the FBI that almost sort of baffles the mind to think how it even continued on and why.

FOX411: A lot of people have seen the trailer, the physical transformation that Johnny Depp did, what was your first reaction when you first saw him like that and then how does that help you as well?
Edgerton: Working with great actors helps actors do greater work. Johnny was someone that I’ve watched ever since I was very young and admired his work so it was exciting to get to work with him. His transformation on the outside is sort of so spot on to what you see and pictures you see of Jim Bulger but then the embodiment of that is very special too. The deep kind of embodiment, of that chilling sort of stillness and silence of his you know, the coiled snake aspect of him which I thought was very special and great to be opposite. Almost to the point where I was like, I know I’m working with Johnny Depp but… where is he? Because it was a great transformation.

FOX411: How did this role stand out for you and in addition, I know it’s so early, but what is your reaction when you start hearing awards buzz or anything like that?
Edgerton: The role came to me just by like luck I don’t know but I feel lucky that I got to play John because it’s such a kind of interesting character for me. So sort of stuck between two worlds and as the movie progresses there’s the question of he’s sort of trying to backpedal his way out of a lot of scenarios and as an actor that’s great fodder to work with and I got served up every day with these fantastic actors to work with. Almost every one of the actors I get to do some kind of significant stuff with. The whole recognition of the work is fantastic. I would think that it speaks at large to the movie that we’ve made being something that feels elevated or special or something deeply interesting I hope. But yeah that’s just flattering and it’s nice.

Fox News Entertainment Producer Ashley Dvorkin covers celebrity news, red carpets, TV, music, and movies. Dvorkin, winner of the 2011 CMA Media Achievement Award, is also host of "Fox 411 Country," "Star Traveler," "Fox 411 Big Screen," and "Fox on Reddit."