Actor James Gandolfini, Best Known as Tony Soprano, Dead at 51

James Gandolfini, the burly actor best known for his Emmy-winning portrayal of a conflicted New Jersey mob boss in the acclaimed HBO cable television series "The Sopranos," died on Wednesday while vacationing in Rome, the network said.

Gandolfini, 51, who began his career in theater in New York, making his Broadway debut in a 1992 revival of "A Streetcar Named Desire," died of a possible heart attack, HBO spokeswoman Mara Mikialian told Reuters.

Since "The Sopranos" ended its six-season run in June 2007, Gandolfini has appeared in a number of big-screen roles, including the espionage thriller "Zero Dark Thirty" and the comedy "The Incredible Burt Wonderstone."

At the time of his death, Gandolfini had been working on an upcoming HBO series titled "Criminal Justice." HBO declined to elaborate on the series other than to say that it was in development and that Gandolfini was a part of it.

"We're all in shock and feeling immeasurable sadness at the loss of a beloved member of our family," the network said in a statement. "He was special man, a great talent, but more importantly, a gentle and loving person who treated everyone, no matter their title or position, with equal respect."

Gandolfini broke ground with his signature portrait of Tony Soprano, the head of a fictional New Jersey mob family, in "The Sopranos."

As Tony Soprano, Gandolfini created a gangster far different from any previously seen in American television or film. He was capable of killing enemies with his own hands but was prone to panic attacks. He loved his wife, Carmela, played by Edie Falco, and was a doting father, but he carried on a string of extramarital affairs.

He regularly saw a therapist, played by Lorraine Bracco, to work out his anxiety problems and issues with his mother.

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The show, which earned Gandolfini three Emmy Awards as best lead actor in a drama series, was considered by many critics at the time the finest drama to have aired on U.S. television.

Gandolfini's role also paved the way for a parade of popular prime-time shows built around profoundly flawed characters and anti-heroes, from "Dexter" and "Breaking Bad" to "Mad Men" and "Nurse Jackie."

A New Jersey native, Gandolfini worked as a truck driver, bouncer and nightclub manager in New York City before he went to an acting class with a friend and got hooked.

"I'd also never been around actors before," he told Time magazine, "and I said to myself, 'These people are nuts; this is kind of interesting.'"