On July 17, 1992, he was struck by a car while rollerblading. The driver of the car fled the scene and was never identified. Mantlo suffered severe head trauma. According to his biographer, cartoonist David Yurkovich, in 2006, "For a while Bill was comatose. Although no longer in a coma, the brain damage he suffered in the accident is irreparable. His activities of daily living are severely curtailed and he resides in a health care facility where he receives full-time care.".