'The Iceman' Stars Michael Shannon, Winona Ryder on a Killer's Secrets and Lies (Video)

"I think he was filled with rage," says Michael Shannon of the infamous contract hitman who hid his deadly deeds from his family for decades.

The Iceman, an engrossing thriller starring Michael Shannon as Richard Kuklinski, a contract hitman who killed more than 100 people, poses an interesting question for the audience.

Kuklinski was a man with a wife (played by Winona Ryder) and children, who, up until he was finally arrested, seemed to have no idea what the patriarch of the family did for a living.

But how could they not know?

The Hollywood Reporter sat down with the stars of the film to talk about what they'd learned from playing their roles.

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"I think he was filled with rage," says Shannon of Kuklinski, who, between 1948 and 1986, was paid by the mob to kill people. "This was the one thing he had in abundance, this rage. When he was given this opportunity to turn it into a job, he took advantage of it."

Ryder's character may be even more complex than Shannon's.

"My opinion, and it may be different from others, I believe that she did know, to a certain extent," says Ryder of her character. "I don't think it's possible in a marriage for that long in that era of offices and secretaries and not have a clue."

"I do think that she was in very, very deep denial," adds Ryder.

"She seems very fragile," says Shannon of Kuklinski's real-life wife. "Even if she was in denial and there were things she knew and didn't say, who are any of us to judge her? I'm sure it was a very difficult situation."

The Iceman, directed by Ariel Vromen, also stars Chris Evans and Ray Liotta. It hits theaters on May 3.

Watch THR's interview above.

Email: Rebecca.Ford@thr.com; Twitter: @Beccamford