(CNN) -- James Gandolfini, best known for his role as an anxiety-ridden mob boss on HBO's "The Sopranos," died Wednesday while on vacation in Italy. He was 51.
His body is in a hospital morgue in Rome. Once the U.S. Embassy issues a death certificate, Gandolfini's remains can be returned to the United States.
"It is with immense sorrow that we report our client, James Gandolfini, passed away today while on holiday in Rome, Italy," managers Mark Armstrong and Nancy Sanders said in a joint statement. "Our hearts are shattered and we will miss him deeply. He and his family were part of our family for many years and we are all grieving."
The actor had been scheduled to make an appearance at the Taormina Film Fest in Sicily this week.
Gandolfini won three Emmy Awards for his portrayal of Tony Soprano, the angst-wracked mob boss who visited a therapist and took Prozac while knocking off people. "The Sopranos" aired from 1999 to 2007.
Edie Falco, the actress who played Tony's wife Carmela, said she was "shocked and devastated" by the news.
"He was a man of tremendous depth and sensitivity, with a kindness and generosity beyond words. I consider myself very lucky to have spent 10 years as his close colleague. My heart goes out to his family," Falco said in a statement Thursday. "The love between Tony and Carmela was one of the greatest I've ever known."
"Jimmy was the spiritual core of our Sopranos family, and I am stunned at this devastating loss," said Chris Albrecht, the former president of HBO who gave the green light to the show. "He was a great talent, but an even better man. My thoughts are with his family."
HBO is owned by TimeWarner, which is also CNN's parent company.
Actor Steve Van Zandt, who played Tony Soprano's confidant Silvio Dante, felt equally close to Gandolfini in real life. "I have lost a brother and a best friend," he posted on Twitter. "The world has lost one of the greatest actors of all time."
Gandolfini was born September 18, 1961, in Westwood, New Jersey, according to Biography.com.
He graduated from Rutgers University and, as the story goes, worked as a bartender and a bouncer in New York City until he went with a friend to an acting class.
He got his start on Broadway, with a role in the 1992 revival of "A Streetcar Named Desire" with Jessica Lange and Alec Baldwin.
Gandolfini's big screen debut came in the role of a heavy in the bloody "True Romance" in 1993.
His breakthrough on the small screen came in 1999 with the role of Tony Soprano.
"He was a genius. Anyone who saw him even in the smallest of his performances knows that," David Chase, who developed "The Sopranos," said in a statement. "...A great deal of that genius resided in those sad eyes."
Gandolfini, who was notoriously press shy, had a reputation in the tabloids for being sometimes difficult.
"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," Chase said.
While Gandolfini was known for sometimes ruthless, often imposing characters, those who worked with him described an actor who put his heart into a role.
"He was just so good at the emotion. A very passionate man and a very, very tender man," Matthew Warchus, who directed Gandolfini in the 2009 Broadway play "God of Carnage," told CNN. "I really loved him and admired him a great deal."
Larry King, who saw Gandolfini in Las Vegas just weeks ago, told CNN the actor was "jovial and seemed happy."
"He stamped himself in 'The Sopranos' so much, people have overlooked his many diversified roles he's performed," King said. "He was a very diverse character actor, who became a star."
IReporter Shana O'Neil worked in an office, where Gandolfini was shooting in 1994. She remembers him as "Jersey through and through" with a great smile. "I just always think of him as that guy."
His Sopranos fame, she said, changed nothing about the way she remembers him.
Gandolfini's acting credits included roles in "The Last Castle" with Robert Redford, "The Mexican" with Brad Pitt and Julia Roberts, and "Surviving Christmas" with Ben Affleck.
In recent years, he had starred in several movies, including the Oscar-nominated "Zero Dark Thirty," "The Taking of Pelham 1 2 3" and "Killing Them Softly."
Gandolfini was also known to children, voicing Carol, a wild thing, in the 2009 movie adaptation of Maurice Sendak's classic "Where the Wild Things Are."
He took to the stage to do a reading of Sendak's "In The Night Kitchen" to mark the author's 80th birthday.
News of the actor's death spread quickly, drawing shock and sadness from those who had worked with him.
"James Gandolfini was a kind, funny, wonderful guy. I'm so lucky to have worked with him. Sending love to his family. Such a sad, sad day," Olivia Wilde, who starred with the actor in "The Incredible Burt Wonderstone," said in a post on Twitter.
Actor Steve Carell of "Office" fame, who also appeared in "Wonderstone", simply said on Twitter: "James Gandolfini. What a great loss."
New Jersey Gov. Chris Christie described himself as a "huge fan" of Gandolfini.
"It's an awful shock. James Gandolfini was a fine actor, a Rutgers alum and a true Jersey guy," he said.
If his managers are right, and he died of a heart attack, it struck much too early, said CNN's chief medical correspondent, Dr. Sanjay Gupta.
"(The) average age of someone having a first heart attack -- if this is in fact what we're talking about -- is usually in the mid-60s," he said.
Risk factors such as smoking, lack of exercise, obesity and high cholesterol can lower the age range significantly, according to Gupta.
Gandolfini is survived by his wife, Deborah, and their 9-month-old daughter, Liliana. He is also survived by a son, Michael, from another marriage.
CNN's KJ Matthews, Douglas Hyde, Elise Miller and Henry Hanks contributed to this report.