Jung was last seen in Everett, Washington on September 25, 2005. He has never been heard from again. Authorities believe he went for a hike in the Cascade Mountains. He is an experienced and passionate mountain climber, but when he went on climbs he would often not tell other people where he was going or when they should expect him to return. An extensive search turned up no sign of him. Jung's red 1990 Jeep Cherokee with the license plate number 421PDV disappeared with him.

Jung grew up in Kirkland, Washington. He has a bachelor's degree from the University of Washington and a graduate degree from the University of California at Berkeley. He lived alone at the time of his disappearance and kept to himself. His family stated he was happy with his life and had no reason to walk away from it. His case remains unsolved.