Terrible news for TV fans: James Gandolfini, who played mobster Tony Soprano on HBO's seminal drama "The Sopranos," died suddenly today at the age of 51.

Gandolfini was traveling in Rome on vacation before a scheduled appearance at Sicily's Taormina Film Festival when he fell ill; conflicting reports have him suffering either a heart attack or a stroke.

HBO confirmed his death in a statement: "We're all in shock and feeling immeasurable sadness at the loss of a beloved member of our family. He was a 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. He touched so many of us over the years with his humor, his warmth, and his humility. Our hearts go out to his wife and children during this terrible time. He will be deeply missed by all of us."

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Gandolfini won three Emmys, three SAG Awards, and one Golden Globe for his performance as Tony Soprano on the acclaimed HBO drama — a complex, sometimes villainous role that launched the current wave of TV antiheroes. "The Sopranos" remains HBO's highest-rated series ever, with 13.4 million viewers tuning in for the Season 4 premiere in 2002.

"Sopranos" creator David Chase lauded Gandolfini in a statement: "He was a genius. Anyone who saw him even in the smallest of his performances knows that. He is one of the greatest actors of this or any time. A great deal of that genius resided in those sad eyes. I remember telling him many times, 'You don't get it. You're like Mozart.' There would be silence at the other end of the phone...He wasn't easy sometimes. But he was my partner; he was my brother in ways I can't explain and never will be able to explain."

His "Sopranos" shrink, Lorraine Bracco, was stunned by the news, saying, "We lost a giant today. I am utterly heartbroken." Tony Sirico, who played Tony's right-hand man Paulie Walnuts, mourned the loss of "one of my best friends in life. He helped me with my career and I’m going to miss him. He’s part of my family.” And Steven Schirripa, who played Tony's brother-in-law Bobby Bacala, added: "Jimmy was a dear friend and like a brother to me. He was a great actor and a great father. I will miss him terribly. I am very sad."

In addition to "The Sopranos," Gandolfini appeared in dozens of movies, including memorable supporting turns in "True Romance," "Get Shorty," and last year's "Zero Dark Thirty." He was also an accomplished stage actor, joining Alec Baldwin and Jessica Lange in the 1992 revival of "A Streetcar Named Desire" and scoring a Tony nomination in 2009 for his role in the smash hit drama "God of Carnage."

Jeff Daniels, Gandolfini's co-star in the latter production, fondly remembered the late actor. "If Broadway has a version of a guy you want in your foxhole, Jim Gandolfini was mine," Daniels said in a statement. "During our time together in 'God of Carnage,' we played 320 performances together. He didn't miss one. Sadly, I now miss him like a brother."

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Born in Westwood, New Jersey, in 1961, Gandolfini was raised in a devoutly Roman Catholic home by two Italian-speaking parents. He appeared in plays in high school and later attended Rutgers University, working as a bouncer at an on-campus bar. (After hitting it big, Gandolfini became a booster for his alma mater, donating money and appearing in commercials for Rutgers football.) While living in New York City, he tagged along with a friend to an acting class and felt so exhilarated, he knew he had to come back.

Gandolfini built an admirable film career in the '90s but never approached stardom until Chase cast him as Tony Soprano. And even then, he didn't think he deserved it. "I thought that they would hire some good-looking guy,” he told Vanity Fair last year. “Not George Clooney, but some Italian George Clooney, and that would be that." In fact, HBO did approach "GoodFellas" star Ray Liotta about the role, but Liotta wanted to concentrate on movies. So Gandolfini got the nod.

His relationship with HBO continued after "The Sopranos" ended in 2007. He produced a pair of probing documentaries for the network, "Alive Day: Home From Iraq" and "Wartorn: 1865-2010," about the challenges soldiers face after returning home from war. And Gandolfini was slated to star as a defense attorney in HBO's upcoming miniseries "Criminal Justice"; the network ordered a seven-episode limited run last month.

The actor's life off-screen wasn't nearly as charmed. During his "Sopranos" run, he split from his first wife, Marcy Wudarski. In the midst of their divorce, Wudarski made explosive claims that Gandolfini had multiple mistresses and absued drugs. He eventually confirmed that he logged at least one stint in rehab for his drug habit, but insisted he was sober.

He also was involved in a scooter accident in New York, resulting in knee surgery that temporarily postponed shooting on "The Sopranos'" final season.

Gandolfini is survived by his wife, Deborah Lin, their 8-month-old daughter, Liliana, as well as a son, Michael, from his previous marriage.

Gone too soon, James Gandolfini was my Hero, and a true friend, who inspired me by his role in the Soprano Series. I am saddened by this loss and will never forget 'Tony Soprano'. He was a true friend of mine.

Tony soprano...badest boss ever liveth. RIP

James Gandolfini was an INCREDIBLE actor.His powerhouse portrayal of "Tony Soprano" made me fall in love with the show.From the gritty opening sequence of him driving his car with the song "woke up this morning" blaring,to the love he had for his children,to his blazing temper,ruthless business mindset,his playful nature and aggressive arguments with his wife,sister and mother.Great actor,humble man.He will live forever in my memory."Woke up this morning got myself a gun,woke up this morning and all my love had gone....."