*This story was updated at 9:50 a.m. Tuesday, Aug. 17*

SUBLETTE COUNTY – The one hiker who was reported missing over the weekend was discovered by authorities at approximately 5:15 p.m. on Monday. Authorities confirmed that, unfortunately, they discovered the hiker returning from Gannett Peak was discovered deceased in Fremont County.

More information will be made available after the Sublette County Sheriff's Office collaborates with Fremont County Sheriff's Office.

Thor Hallingbye, 41, was last seen Saturday afternoon, Aug. 14, by members of his group as he descended Gannett Peak in the Wind River Mountains.

A call came from the International Emergency Response Center on Sunday, Aug. 15, at 11:14 a.m. that Hallingbye was missing, according to Sgt. Travis Bingham. Tip Top Search and Rescue members flew the county’s leased helicopter Sunday looking for him and were out again Monday with a team searching on the ground as well, he said.

The group had hiked from Green River Lakes and spent a night camping before Hallingbye was last seen. He was wearing a bright red backpack

Hallingbye is 5 feet, 7 inches tall, weighs about 125 pounds and has blue eyes and light brown hair. Flyers were posted online and at the trailhead; anyone with information is asked to call the Sublette County Sheriff’s Office at 307-367-4378.

TTSAR evacuated several hikers to the Pinedale Medical Clinic throughout last week due to altitude sickness, with vomiting, dizziness and faintness, Bingham said.

Om Aug. 9, at 12:41 p.m., a man reported that his wife and a friend in their late 20s went in to May’s Lake on Aug. 6. The friend became extremely ill and was taken by helicopter to the clinic.

At 1:03 p.m. Sunday, a woman called, worried about friends hiking on Aug. 7 from Green River Lakes to Square Top Mountain and due back in Utah on Aug. 8. Eventually they all made contact and it turned out everyone was fine, Bingham said.

On Tuesday, Aug. 10, a call came in about a man with an injured knew but he was brought out on horseback without calling in TTSAR.

Two more very ill hikers with altitude sickness were evacuated by helicopter to the clinic that day, the first a 37-year-old man and the second a 67-year-old woman camping near Two Top Lakes.

Altitude sickness hits people who might be fit but are not properly acclimated to the high elevations in the mountains, Bingham said.

He urges people going into the mountains to go to the Sublette County Sheriff’s Office website or use the SCSO app to fill out a “wilderness check-in” with travel and contact information. Dispatchers keep the information and if a party has not called to say it is out safely, a deputy will follow up on the people.

“The last few weeks we’ve really seen it taking off,” he said of the check-in. “If something happens to you, it gives us a place to start.