The Tsuyama massacre (津山事件, Tsuyama jiken) was a revenge spree killing that occurred on 21 May 1938 in the rural village of Kamo close to Tsuyama in Okayama, Empire of Japan. Mutsuo Toi (都井 睦雄, Toi Mutsuo), a 21-year-old man, killed 30 people, including his grandmother, with a Browning shotgun, katana, and axe, and seriously injured three others before killing himself with the shotgun. It is the deadliest shooting by a lone gunman in Japanese history.