"The Sopranos" star James Gandolfini has died at the age of 51.

The three-time Emmy winner's managers Mark Armstrong and Nancy Sanders confirm that Gandolfini died while on vacation in Italy. Cause of death is believed to be a heart attack.

"It is with immense sorrow that we report our client James Gandolfini passed away today while on holiday in Rome, Italy," Armstrong and Sanders state. "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."

When David Chase cast Gandolfini as anxiety-prone mobster Tony Soprano, Gandolfini was a veteran character actor best known for roles in films like "Get Shorty," "Crimson Tide" and "True Romance," but he became an immediate star when "The Sopranos" premiered in in 1999. 

"He was a genius. Anyone who saw him even in the smallest of his performances knows that," Chase said in a statement. "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. For Deborah and Michael and Lilliana this is crushing. And it's bad for the rest of the world. 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."

Through Gandolfini's portrayal, Tony Soprano became one of the iconic characters in television history and the actor was nominated for six acting Emmys, winning in 2000, 2001 and 2003.

Gandolfini was also nominated for four Golden Globes, winning one. He also won three individual Screen Actors Guild Awards as an individual and two more as part of the "Sopranos" ensemble. The Television Critics Association honored Gandolfini with the group's Individual Achievement in Drama award in 1999, 2000 and 2001, the only actor to win three awards in the category.

In a statement, HBO says, "We're all in shock and feeling immeasurable sadness at the loss of a beloved member of our family.  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.  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."

Adds Chris Albrecht, who headed HBO during the run of "The Sopranos," "Jimmy was the spiritual core of our Sopranos family, and I am stunned at this devastating loss. He was a great talent, but an even better man. My thoughts are with his family."

Since "The Sopranos" ended, Gandolfini has worked in a producing capacity for HBO, earning Emmy nods for the documentary "Alive Day Memories: Home From Iraq" and the telefilm "Hemingway and Gellhorn," while the premium cable network made multiple attempts to develop new series projects for him to act in.

Feature credits for Gandolfini included "In the Loop," "The Taking of Pelham 1 2 3," "Where the Wild Things Are" and "Killing Them Softly." Gandolfini was most recently seen in David Chase's feature directing debut "Not Fade Away" and in "The Incredible Burt Wonderstone." He had been working on Fox Searchlight's "Animal Rescue" opposite Tom Hardy and Noomi Rapace.

Gandolfini is survived by wife Deborah Lin, daughter Liliana, born in October, and teenage son Michael.

Stay tuned, obviously, for more details as we learn them.