would have killed her, but they were down around my ankles and i couldn't get them loose. >> sheriff reichert and the other task force members wanted to learn not just the how of the green river murders, but, also, the why. a career spent chasing the devil, as reichert's new book is called, recovering the mangled bodies of teenage girls creates a powerful incentive to understand what forces forge a serial killer. >> over those years, those visions are very fresh. those images are burned into your mind forever. >> it turns out there were other opportunities to stop gary ridgway from killing that had been missed. his violent acts began years before, way back in his teen years. could something have been done back then? weeks of questioning brought forth secrets from ridgway's childhood and the story of his first attack. in his first interview, gary ridgway's youngest victim tells "dateline" his story of encountering and surviving an