A 60-year-old Denver man died while on a commercial rafting trip on the Green River in Dinosaur National Monument Saturday.

According the National Park Service, it is currently believed that he suffered some sort of cardiac event after falling into the water.

The man, who has not been identified, was on a multi-day rafting trip with Sheri Griffith Expeditions, a certified rafting company out of Moab, Utah.

At around 3:00 p.m. on Saturday the two-person inflatable kayak that he was in flipped while navigating Winnie's Rapid, a class II rapid on the Green River in the Canyon of Lodore in the Colorado portion of Dinosaur National Monument.

Witnesses told the National Park Service that after the man fell into the water, they saw him patting his head to indicate that he was okay.

Before he was able to get out of the water, he began to show signs of distress and became unconscious.

According to the National Park Service, he was then pulled from the water and CPR was performed on him. A river guide also made an emergency call to monument staff.

A Classic Air Medical helicopter was able to land in the area and transport the victim to Memorial Hospital in Craig where he was pronounced dead.

An autopsy will be performed to determine an official cause of death. The victim's name will also be released once the family has been notified.