ROCKY MOUNTAIN NATIONAL PARK, Colo. -- A tree fell on two 68-year-old hikers in the Rocky Mountain National Park Tuesday afternoon, killing one hiker and injuring the other.

Park spokesman Larry Frederick said 13 volunteers retrieved the body of the dead hiker about five hours later.

The two hikers were making their way up the Sandbeach Lake Trailhead when "a dead Douglas fir tree, approximately 30 feet from the trail, broke off 15 feet above ground striking both," Frederick said.

One of the hikers was knocked out by the tree but managed to hike out and call for help at the Wild Basin Lodge, which is located at the trailhead.

"He had heard a crash and got hit by a tree and then when he got up to look for his friend, he found his friend underneath the tree in the middle of the trail, with his head against a rock -- no pulse and not breathing," said Frank Waterhouse, a building and grounds manager at the Wild Basin Lodge who helped the hiker contact rescuers.

"He was calm and concerned for his friend, a little shaken but mostly concerned for his buddy," Waterhouse.

It's still not known exactly what caused the tree to fall. Winds gusting up 50 to 60 mph were reported in the area at the time of the accident, Frederick said.

Rangers are not sure though if bark beetles weakened the tree.

The victim has not been identified. He and his hiking partner are both from the Boulder area.