James Gandolfini, who was best known for his portrayal of New Jersey mob boss Tony Soprano in "The Sopranos", died last night while on vacation in Italy at age 51.

He was scheduled to attend the closing of the Taormina Film Festival in Sicily on Saturday, which was one of the reasons for his trip. Mara Mikialian, a spokeswoman for HBO, told sources that he "may" have suffered a heart attack.

His incident occured in his hotel in Rome, where he was immediately taken to the local Umberto I hospital. When he arrived at the hospital, his heart had already stopped. This all occurred at about 11 pm, local time.

Gandolfini may have risen to popularity with The Sopranos, but he has stayed busy since then. He starred in "Zero Dark Thirty" and the crime drama "Killing Them Softly." He had another HBO series and 2 movies due out next year as well.

His roles had typically been harsher, more macho characters, but he expressed a desire to move on from that after The Sopranos. 

"I'm too tired to be a tough guy or any of that stuff anymore," he said. "We pretty much used all that up in this show."