Częstochowa massacre
1939 CE.
Shown on the map at 50.800°, 19.117°.
The Częstochowa massacre, also known as the Bloody Monday, was committed by the German Wehrmacht forces beginning on the 4th day of World War II in the Polish city of Częstochowa, between 4 and 6 September 1939. The shootings, beatings and plunder continued for three days in more than a dozen separate locations around the city. Approximately 1,140 Polish civilians (150 of whom were ethnically Jewish), were murdered.
Text from the Wikipedia article Częstochowa massacre, licensed CC BY-SA 4.0.