When Hosobuchi and his 61-year-old wife reached the waterfall, with the canyon floor about 15 feet below them, Hosobuchi rappelled from an anchor in the waterfall instead of crossing it and rappelling from an anchor on the other side, Baltrus said. His repelling device jammed, possibly because of a knot, and he wound up upside down, his hands about five feet above the ground.
His wife, who had earlier managed to climb down to the canyon floor, tried to help him, but couldn't. And they were the last ones in the canyon, having been passed by several groups throughout the day.
Hosobuchi's wife tried in vain to locate help Tuesday night, but apparently became disoriented about halfway through the nine-mile route in the remote, rugged area.
"The partner was caught by darkness and was unfamiliar with the exit route, and could not make it out of the canyon until Wednesday morning," Baltrus explained.
A canyoneer from a group that had passed the couple earlier in the day had called park dispatchers at 9 p.m. to tell them that at their current pace, Hosobuchi and his wife would probably have to spend the night in the canyon. Based on that, rangers began looking for the overdue couple on Wednesday morning and ran into Hosobuchi's wife on the trail about 11:45 a.m. as she was hiking out.
The park's search and rescue team found the victim about an hour later.
Baltrus said the couple were relatively new to canyoneering, and had not been to the Subway area. Their only experience was an introductory course and completing a trip through Keyhole Canyon, elsewhere in the park.
According to Baltrus, they hadn't mastered route finding and may not have had the skills needed to get out of trouble while rappelling. Rappelling in a watercourse is even more difficult and may have contributed to Hosobuchi's death, Baltrus said in a news release about the accident issued Thursday.
Hosobuchi's death was the first reported in the Subway area in recent memory, park officials said, though rangers have completed four successful rescues in the slot canyon so far this year.
Zion National Park Superintendent Jock Whitworth issued a statement in sympathy and warning.
"The Subway is deceiving. It is a very popular trail, but very difficult the 9-mile hike requires rappelling and ascending skills, extensive route finding experience, and swimming through several cold and deep pools," Whitworth said. "Unfortunately, its location inside the wilderness also means that rescues are not always possible or timely enough. Sound decision making and problem solving are critical."
The Subway, also known as the Left Fork of North Creek, carries a 2B III difficulty grade using the Canyon Rating System, being considered a semi-technical canyoneering challenge. Normally, for experienced canyoneers, it is considered a seven to nine-hour excursion and offers some of Zion's most iconic showcase scenery.
Visitors, having obtained a backcountry permit, can rappel into the slot canyon from above, or hike into it from below.