MARYVILLE, Tenn. (AP) - A Maryville boy is responding well to treatment after being struck by lightning at Yellowstone National Park in Wyoming, his family said.

Twelve-year-old Josh Hughes remained in serious condition in the pediatric intensive care unit of Primary Children's Medical Center in Salt Lake City, said his grandmother, Ramelle Trundle of Maryville. The boy was taken off a ventilator Wednesday and is breathing on his own, she said.

"We're hoping and praying he's going to be OK," Trundle said.

The boy's father, Bill Hughes, said Josh has some pneumonia, likely from inhaling fluid during CPR.

"His heart, lungs and brain are functioning well," Hughes told The Daily Times newspaper of Maryville. "He's still heavily sedated but is responsive. He recognizes us."

Josh and 10 other people were injured Tuesday when lightning struck a boardwalk where a crowd had gathered to watch an eruption of the Old Faithful geyser. Two physicians and a nurse were among the visitors and immediately began CPR on Josh, who suffered full cardiac arrest.

He was flown by helicopter to a hospital in Idaho Falls, Idaho, and later flown in a plane equipped as an air ambulance to Salt Lake City.

The boy's parents, Bill and Sharon Hughes, were in the nearby visitors center at the time of the lightning strike.

Bill Hughes said his son has a burn on his right shoulder blade and singed hair. There also is a hole burned in Josh's shorts where the lightning apparently exited.

"They're watching his kidneys and leg," Trundle said. "His leg is swollen some. It might require surgery."

Doctors also are monitoring fluid in his lungs, she said.

Hughes said he is staying at the hospital with Josh while his wife and their other sons ages 16, 15, 9 and 7 are staying at a Ronald McDonald House in Salt Lake City.

"Josh is a very fortunate boy," Hughes said. "Early CPR and a lot of prayer have helped.

"Now, we just have to wait while his condition improves, and we have every reason to believe it will. There are a lot of people praying for him, and we really appreciate that. We hope to be able to bring Josh home soon."