Channel 2 (ni-channeru) is the single most widely known free access Japanese Internet bulletin board forum, with over five million people accessing it each month. With its many dysfunctional aspects, Channel 2 is a synonym for the chaos of the Internet in Japan. This study analyzes the dynamics among users of the Channel 2 forum, focusing specifically on the dissemination of alarming images and video files of the October 2004 Japanese hostage murder in Iraq. An examination was conducted of November 2004 Channel 2 threads and entries about the dissemination of images and video files of the hostage murder. Our analysis reveals how content that highly violated moral principles appeared and how a self-regulating mechanism by the user community functioned pro-socially in an uncontrolled, anonymous Internet forum. These findings contrast with previous studies that predicted asocial or antisocial behavior in anonymous online environments.