Autopsy results confirm that Sopranos star James Gandolfini suffered a heart attack and died of natural causes on Wednesday, June 19, a hospital source told Reuters early Friday. The 51-year-old's sudden death instantly shocked and saddened fans worldwide. As previously reported, Gandolfini had been visiting Rome with family ahead of a scheduled Saturday appearance at the Taormina Film Festival in Sicily.

PHOTOS: Stars we've lost in 2013

In a heartbreaking detail, the star's manager confirmed that Michael, Gandolfini's 13-year-old son, found his father collapsed in his hotel room and immediately alerted hotel staff about the medical emergency.

The three-time Emmy winner was then transported to the Policlinico Umberto I hospital; Dr. Claudio Modini told Reuters and other outlets that paramedics attempted in vain to revive Gandolfini en route to the hospital.

PHOTOS: Stars gone too soon

"The resuscitation maneuvers, including heart massage, continued for 40 minutes and then, seeing no electric activity from the heart, this was interrupted and we declared James dead," Dr. Modini said.

PHOTOS: Famous fathers in Hollywood

Hollywood has been grieving the actor ever since news break of his death late Wednesday. "James was such an enormous talent, and an even greater spirit. I will be forever grateful for the privilege of working with him, and shall cherish his memories always," said Katheryn Bigelow, who directed Gandolfini in Zero Dark Thirty.

This article originally appeared on James Gandolfini Autopsy Results: He Died of Heart Attack, Natural Causes