A Whitefish man died while traveling on the Going-to-the-Sun Road in Glacier National Park over Labor Day weekend.

The man, 64, who was the passenger in a vehicle was found unresponsive and is believed to have died from a heart attack, according to a press release from the park service. The man was declared dead at the scene.

Glacier Park rangers at about 3 p.m. on Monday responded to a 911 call of an unconscious man just west of Lake McDonald Lodge on the Sun Road. The medical emergency temporarily restricted traffic for three hours while personnel responded.

Park rangers, Three Rivers Ambulance, ALERT air ambulance, and medically qualified bystanders administered CPR and other emergency medical treatment.

The ALERT helicopter landed on the Sun Road briefly stopping traffic before vehicles were routed around the incident in the far lane of travel until about 6 p.m. While death is believed to be from natural causes, park officials noted, a statement was released due to the number of people who witnessed the incident.