California, Yosemite National Park. On 21 August Peter Ullrich (17), and Allen Harris (15) and two skiers were attempting to scale 3rd and 4th class cliffs east of Tenaya Creek Bridge. Their companions turned back. Ullrich and Harris continued on since they were unable to descend without difficulty. Ullrich slipped on slabs and loose rock and fell several hundred feet to his death.
Source: Steve Hickman, Yosemite National Park.
Analysis: All were inexperienced and inadequately equipped, and demonstrated poor judgment and a lack of common sense.