William Hasley, a prominent figure in the entertainment industry and biographer of Caitlyn Jenner, was found dead at the age of 78 while hiking in Runyon Canyon, Los Angeles. He collapsed off Nichols Canyon Road on Saturday evening, and despite the efforts of air rescuers, he was declared dead shortly after 6:42 PM. The exact cause of his death is currently unknown. Hasley authored Jenner's 1996 self-help book, 'Finding the Champion Within,' and had a successful career as a screenwriter for major studios like Universal Pictures and Warner Brothers. He was also known for his brief marriage to actress Robin Riker in 1987. In addition to his writing career, Hasley taught screenwriting at UCLA and was actively involved in community service. This tragedy follows another recent loss for Jenner, whose confidante Sophia Hutchins died in July 2025 after a fatal accident.