Anaconda Road Massacre
1920 CE.
Shown on the map at 46.017°, -112.530°.
On April 21, 1920, during a miners strike in Butte, Montana's copper mines, company guards fired on striking miners picketing near a mine of the Anaconda Copper Mining Company, killing Tom Manning and injuring sixteen others, an event known as the Anaconda Road massacre. His death went unpunished.
Text from the Wikipedia article Anaconda Road massacre, licensed CC BY-SA 4.0.