RAPID CITY, S.D. (AP) — A man who was hiking on an unmarked trail in southwestern South Dakota that was featured in a social media challenge died when he and another hiker ran out of water.

The Pennington County Sheriff’s Office said 22-year-old Maxwell Right, of St. Louis, was hiking in Badlands National Park on Wednesday when he collapsed and died of suspected dehydration and exposure.

A 21-year-old man from Missouri who was hiking with Right was flown to a Rapid City hospital, where he was placed under observation for exposure and dehydration.

The weather in the park has approached 100 degrees most of the week. Pennington County has put out numerous public service announcements warning hikers to be prepared for the elements and stay on marked trails.