A Colorado man died after flipping an inflatable kayak on the Green River in Lodore Canyon of Dinosaur National Monument/NPS file photo

A Colorado man who initially appeared OK after flipping an inflatable kayak on the Green River in Dinosaur National Monument later died, possibly of a cardiac event.

Park officials said Sunday that the 60-year-old man was on a multi-day commercial river trip through the Canyon of Lodore when he capsized his kayak around 3 p.m. Saturday.

Monument staff received a call shortly after the incident that CPR was in progress on a client with Sheri Griffith Expeditions, an authorized river concessionaire based out of Moab, Utah. The client was in a two-person inflatable kayak that flipped in Winnie’s Rapid, causing him to enter the water. Witnesses observed him giving the “head pat” signal to indicate he was okay as he continued to float downstream, a park release said Sunday.

"Before he was retrieved from the water, he showed signs of distress and became unconscious. He was pulled from the water and CPR was initiated," the release added. "A river guide on scene made an emergency call by satellite phone to request medical assistance. A Classic Air Medical helicopter from Vernal, Utah, was able to land on site below Winnie’s Rapid," but the man could not be revived.

The victim’s body was transported to the Memorial Hospital at Craig, Colorado and later transferred to the Moffat County coroner. An autopsy will be conducted to determine cause of death. The name of the victim was withheld until the family has been notified.

Winnie’s Rapid is a class II rapid located on the Green River in the Canyon of Lodore in the Colorado portion of the national monument. It is approximately 3.5 river miles downstream of the Gates of Lodore boat launch near the monument’s northern boundary. Flow rates for the Canyon of Lodore section of the Green River, which are influenced by the water release at Flaming Gorge Dam, were averaging 8,600 cubic feet per second.