Actor James Gandolfini passed away in Italy on Wednesday, according to reports by HBO, Variety magazine, TMZ, the New York Daily News and other media outlets. He was 51 years old.

His passing came as a shock to many fans of the talented actor, best known for playing mob boss Tony Soprano on HBO's hit show "The Sopranos," which aired its final episode in 2007.

A source said the three-time Emmy Award winner suffered a "massive heart attack" that led to his death, the Daily News reported.

The official cause of death has not been ruled yet, as his death was so recent, but Variety reports that it was caused by "a possible heart attack."

TMZ reported that Gandolfini is "believed to have suffered a heart attack" and that he was in Sicily for the Taormina Film Festival, where he was scheduled to participate in a festival event.

"Everyone is in tears," a source close to Gandolfini told the Daily News.

Gandolfini, a native of Westwood, N.J., was a beloved actor who had also performed in movies including “Mr. Wonderful,” "Zero Dark Thirty" and “True Romance” and on the stage in plays including 2009's Tony Award-winning Broadway show "God of Carnage."

He is survived by his wife, former model Deborah Lin; a daughter born in October 2012; and a teenage son named Michael, from his previous marriage to Marcy Wudarski, whom he divorced in 2002.