A 15-year-old Boy Scout (search) on an overnight camping trip died after he was thrown from a raft and swept away by a harsh undertow, authorities said.

Chase Hathenbruck (search) was pulled from the Animas River nearly five miles downstream from where he fell in Thursday and was pronounced dead at the scene, state police Lt. Jimmy Glascock said.

The river was moving rapidly and the current pulled off Chase's life jacket, said Jan Gimar, a senior district executive for the Boy Scouts of America Great Southwest Council (search). The teen had been sitting on the edge of the raft before he fell.

"The way the leader explained it to me, he was gone before they even knew it," Gimar said.

Another scout who was thrown from the raft was able to swim to shore, Glascock said. The others held on until a rescue boat could reach them.

The scouts had planned to get out of the water before reaching the dangerous area near Lowhead Dam, but were caught too far out, said Troy Brown, Farmington Fire Department deputy chief.

Another Boy Scout is feared drowned this week. Luke Sanburg, 13, of Helena, Mont., fell into the Yellowstone River at at Yellowstone National Park last Friday. Recovery operations are focused on a 14-mile stretch of the river.