"The Columbine Massacre, sometimes called the Columbine Mine Massacre, occurred in 1927, in the town of Serene, Colorado. A fight broke out between Colorado state police and a group of striking coal miners, during which the unarmed miners were attacked with machine guns. It is unclear whether the machine guns were used by the police or by guards working for the mine. Six strikers were killed, and dozens were injured."

From the articleon Serene, CO:

"The area that once was the company town of Serene is now a public landfill in extreme southwestern Weld County, just outside the limits of the town of Erie and the city of Broomfield."