The chopper landed and Beesley stayed on the mountain so the two teens could be transported to safety.
When the chopper returned, Winder said, the pilot could not locate Beesley and then saw him at the foot of a cliff, where he had fallen.
After determining Beesley was deceased, a rescue crew was brought in to retrieve his body. Ultimately, a Life Flight helicopter with a hoist was used to remove the body from the mountain.
Winder said five members of the rescue crew were staying on the mountain overnight due to darkness and will be removed from the mountain Sunday.
The sheriff said Beesley, 34, had been with UHP for 13 years. He lived in Bear River City and was married with three sons.
Preliminary indications are that Beesley may have fallen when he was trying to retrieve a pack of equipment that had fallen, Winder said.
Beesley is the 15th UHP trooper to die in the line of duty. The most recent prior death was Lt. Thomas Rettberg who was killed flying a department helicopter in 2000.