Columbine Mine massacre: Striking coal miners are allegedly attacked with machine guns by a detachment of Colorado state police dressed in civilian clothes.

The Columbine Mine massacre occurred in 1927, in the town of Serene, Colorado. In the midst of the 1927–1928 Colorado Coal Strike across the state, workers had been picketing one of the few remaining operating mines, in Serene. A fight broke out between Colorado state militia and a group of…