SANDPOINT — Bonner County Sheriff’s officials are continuing their investigation into an apparent skiing accident which killed a 15-year-old on Tuesday.

An autopsy was planned for Wednesday at Providence Holy Family Hospital in Spokane, Wash.

Finer details of the mishap which killed William C. Johnson emerged on Wednesday. A cause of death, however, is still pending, said Bonner County Sheriff’s Lt. Doug Harris.

Johnson, a Sandpoint High School sophomore, was found unconscious and unresponsive in a tree well by two snowboarders riding in Schweitzer Mountain Resort’s south bowl at about 11:50 a.m., according to sheriff’s officials.

The snowboarders extracted Johnson and went for help. Schweitzer Ski Patrol received the call at 12:15 p.m. and arrived at the scene at 12:32 p.m. Patrollers began CPR and took Johnson to the resort’s first aid station, where life-saving efforts continued without success.

A physician on scene pronounced Johnson dead at 1:24 p.m.

Johnson, who was wearing a helmet, reportedly struck a tree while descending C Chute and fell into the tree well in an inverted position. Schweitzer records indicated Johnson’s lift pass was last scanned at 11:15 a.m.

“He was with some other people. They started the run and the others got to the bottom, but he didn’t,” said Harris.

Johnson’s companions were apparently unaware he had fallen and did not notify anybody that he was missing, Harris said.

The area where Johnson fell was heavily treed and Harris said rescuers reported encountering chest-deep snow when they stepped off their skis to tend to Johnson.

Tree wells are naturally occurring voids that can form around the bases of trees in forested areas where deep powder falls. Low-hanging branches keep snow from consolidating around the base of tree and can conceal the depression.

Loose snow within the tree well becomes a suffocation hazard, especially if the person falls into the well head first. The hazard can increase as the person struggles to escape the well.

Schweitzer has not had a skiing-related fatality in at least nine years. A skier from Spokane died of internal injuries after hitting a tree on White Lightning in February 2000. A skier from California was killed after striking a tree on Kaniksu in December 2000.

Lake Pend Oreille School District officials arranged for counselors to be at the school on Wednesday to help classmates.

“Our goal was just to have the doors open and if kids needed some assistance it would be available,” district Superintendent Dick Cvitanich said on Wednesday.

More than 30 students met with counselors, youth ministers and other adults at SHS, Cvitanich said. The group of students included a contingent of the school’s cross country team, of which Johnson was a member.

Counselors will also be on hand when classes resume on Jan. 4, 2010.

“It’s hard for those kids who knew him well,” said Cvitanich.