Tsuyama massacre
Refers to the 1938 revenge spree killing of 30 people in Tsuyama, Okayama Prefecture. Used as a proper noun for this specific historical event.
The Tsuyama massacre is a mass murder that occurred in Tsuyama, Okayama Prefecture in 1938.
Named after the location (津山, Tsuyama) and the nature of the incident (事件, incident).