Actress Cecile De France and French-Algerian actor Kad Merad (L) pose during the red carpet of the movie "Superstars" at the 69th Venice Film Festival August 30, 2012.[Photo/Agencies]

Loving father and husband at home, a ruthless killer at work: The real-life Mafia hit man who inspired Ariel Vromen's new film, "The Iceman," had a steep after-work decompression curve.

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"The Iceman," which premiered Thursday in competition at the Venice Film Festival, dissects the duality of the real life of Richard Kuklinski, who for decades killed on order while keeping the truth of his occupation from tainting his perfect suburban family life.

The movie stars Michael Shannon, the film world's latest Mafia hit man, Winona Ryder as his unsuspecting wife and Ray Liotta as the Mafia boss who sees hit-man potential in Kuklinski's dispassionate coolness and absence of fear.

Vromen said he was captivated when he saw Kuklinski, who was arrested in 1986, tell his story a 2006 documentary. He said he found himself surprised to feel empathy for a man eventually convicted of at least 100 mob hits and who may have committed more than twice that number.

All the while, Kuklinski created an idealized home life for his wife and two daughters, whom he sent to Catholic school and took on roller skating outings.

"I couldn't stop thinking about it, about why did I care about that really, really extreme monster? And it was haunting me, the fact that I did care, that I had a very, very deep empathy," Vromen said in an interview.

"It was quite a challenging struggle to write a script that would be balanced enough, to show on the one hand that this is the devil, and on the other hand not try to be corny and be an apologist for a character like that.

Vromen said he fought for two years to get Shannon for the role, warding off "the obvious choices".

"Michael Shannon comes with a darkness," Vromen said. "If he comes with darkness, my job is to be, how can I lighten that darkness? How can I make that darkness more refined?"

In a sign that Vromen was onto something, Shannon's two-year-old screen test for the role has gotten over 200,000 hits on YouTube.

"Every time I look at Kuklinski, I see the little boy he once was, and I try to imagine all the fear he had to endure as a child. I also see someone filled with self-loathing," Shannon said. "The one thing he did have in excess was rage. Rather than take it out on bystanders, he takes it out on people who, at the end of the day, weren't so innocent."

While Liotta joined the Hollywood hit men parade with his turn in "Goodfellas," Vromen said choosing him to play Mafia boss Roy Demeo was anything but typecasting.

"Ray didn't do a gangster for quite a long time," he said. "(But) I had to find the guy in Hollywood scarier than Michael Shannon."

Demeo's loyal underling is played against type by David Schwimmer.

"I said 'No, no, no! I can't have Ross from 'Friends' in the movie,'" Vromen said. Then Schwimmer sent pictures of him in makeup and the director saw that "he will do everything and anything to fit in," just like the character: a Jewish guy who wants to be a mobster.

For Ryder, playing the seemingly clueless wife meant she had to purge anything she already knew about Kuklinski, rip out all the script pages dealing with his mob activities and stay clear of the set on days they were filming his criminal side.

She didn't, however, attempt to reach out to the real life Deborah Pellicotti, who has denied any knowledge of her husband's activities and has since changed her name, because "I just don't know what I would have learned that much from her."

While Ryder played the unsuspecting wife, she is not entirely persuaded that was the case.

"I don't think you can be married for that long and go to sleep every night with someone, especially when he is getting up in the middle of dinner and going out and killing ... she's doing laundry, there's got to be blood," Ryder said.

Vromen said the only contact he's had with the Kuklinski family is on Facebook with the older daughter.

"She personally is so in love with her father," Vromen said. " She said it was very, very tough on her and the family to realize who he was, but it didn't take away the love she had. Until today, she refused to read any book or any article or any document about him."

He asked if she would see "The Iceman" and there was silence.

"And I said, 'Well, we got the answer,'" he said.