Carleton was last seen in Newcomb, New York on October 9, 1993. He left home residence at 6:00 a.m. for a three-day solo hike in the High Peaks area of the Adirondacks. He was carrying a teal backpack at the time of his disappearance. He didn't take a tent or a camp stove; he planned to stay in lean-tos along the trail. Two hikers believe they shared a lean-to on Indian Pass Trail with Carleton on the day of his disappearance. He told them he was going up Indian Pass. This is the last sign of Carelton; he has never been heard from again. It was raining on the day he vanished and that night it started snowing.

Carleton worked as a psychologist at the state prison in Auburn at the time of his disappearance. He lived with his wife and young daughter in Skaneateles. His case is unsolved and he is presumed to have gotten lost in the wilderness.