The boys were on the trip with family and members of Calvary Chapel East Anaheim. The group from Southern California took a break at the Vernal Fall Footbridge after hiking on Wednesday when the two boys lost their footing and were swept away.
The 10-year-old was pulled from the river by a park visitor about 150 feet away, but CPR failed to revive him. He was pronounced dead at about 3 p.m.
Park rangers are searching between Vernal Fall Footbridge and Happy Isles for the missing 6-year-old brother, who is presumed dead. The boys' mother remains hospitalized. She was hurt trying to rescue her sons.
The rangers are not releasing the boys' names, but there are new missing posters up asking for help locating 6-year-old Jacob Adams.
The pastor of the church said the camping trip started Monday and was supposed to end Saturday. Fellow parishioners said they are all relying on their faith.
"My heart was grieved. My wife and I have two daughters. This couple had two sons. I can't imagine going through what they are going through," said parishioner Paul Eumurian. "I'm confident everybody who knows about it is praying for them. Our confidence here is that God works in ways we don't understand."
The Mist Trail remains open during the search-and-rescue operations, but portions of the trail may close to accommodate search efforts.
Last year, three people went missing above Vernal Fall.
A fund has been set up for the Adams family. For more information, visit http://cc-ea.org/israel-tour/.