He'd been so excited about the trip to Yellowstone National Park (search) — camping under the stars, hiking in the mountains, hanging out with his buddies and fellow Boy Scouts (search).

But what was supposed to have been a fun trip for 13-year-old Luke Sanburg (search) has turned into a tragic ordeal for his family. Luke was feared drowned Monday, three days after falling into the brisk, fast-moving Yellowstone River and being swept toward a rapid.

Yellowstone National Park officials said the focus of the scaled-back search effort had shifted from rescue to body recovery. "I think the family has come to that realization right now," incident commander Tim Reid said.

A family spokeswoman tearfully spoke of Luke on Monday in the past tense, describing him as an outdoor enthusiast, a devoted brother, and a smart boy with sharp sense of humor.

"He was fun to be around, he was as kind a young man and considerate as you'd ever want to meet," said JeNae Lay, an aunt.

Early Friday evening, Luke and other boys from Troop 208 from Helena, Mont., were pushing logs into the river when a log hit him and pushed him off into the 50-degree water, park officials said. Luke, who could swim, was only wearing shorts, tennis shoes and a cap. Shoes believed to be his were found over the weekend.

Reid called the river conditions "unswimmable."

Seven Scouts, including Luke, and three adults were on the trip. One of the boys and a group leader, hiked six or so miles from the backcountry campsite in northern Yellowstone where the group was staying to call for help.

Hundreds of volunteers joined park officials in the search over the weekend, scouring a 14-mile stretch of the river. Kayakers were used as well, though Reid said the high water hampered their efforts. As water levels recede, he expects them to be used again, perhaps late this week.

Park spokeswoman Cheryl Matthews said air and ground searches would continue, with decisions made on a day-to-day basis. As the holiday weekend approached, park officials also were contacting local outfitters and guides to ask them to report anything they might find related to the teen, she said.

Lay said the family has been overwhelmed by the response to Luke's disappearance. Luke's parents have both participated in searching for their son, she said.

"Luke was young man of incredible faith and spiritual maturity who loved and obeyed God as he'd been taught, and he'd been taught that by good parents," she said.

Lay said the family has experienced a wide range of emotions during the past several days and is now trying to deal with the realization that Luke may be dead. "They've said frankly, sometimes drowning victims are never found," she said. "We'll deal with that one day at a time."