Michael Shannon has revealed that he doesn't mind playing intense or unhinged characters on screen - although he confessed it can be "troubling".
The 38-year-old - who played Federal Prohibition Agent Nelson Van Alden in Prohibition-era series Boardwalk Empire and John Givings in Sam Mendes's Revolutionary Road, for which he received an Oscar nomination - portrays real-life contract killer Richard Kuklinski in Ariel Vromen's film The Iceman.
"It's certainly not fun, it's not a happy-go-lucky experience. It's troubling," he admitted.
"Any time I take a job, I'm not afraid to dig into something, no matter how ugly it may be. Those, unfortunately for better or for worse, tend to be the most interesting stories. People are fascinated by them."
"I would shoot all day and then go home and be by myself at night," he said.
"You get into a zone, like a tour of duty. You can't quit as you're being paid. I just try to conserve my energy. I don't goof off a lot on set. If I'm not in front of the camera, I just eat carrot sticks and keep quiet. It was a big responsibility playing this character. So, the fact they thought I could do it, I was pretty honoured by that even though it was dark."
The Kentucky-born actor liked the fact that The Iceman was more of a character study than a glamorous Mob movie.
"I wasn't interested in making a Mob picture. I feel like all the best Mafia movies have already been made and I don't see how anyone is going to make a better one. But I did think Kuklinski was an unusual person that merited consideration or contemplation," he said.
:: The Iceman opens in cinemas on June 7.