Athens Polytechnic March of 1980
The Athens Polytechnic March 1980 was a demonstration held for the 7th anniversary of the Athens Polytechnic Uprising. During the demonstration serious clashes between the protestors and the riot police occurred, during which the "Units for the Reinstatement of Order (MAT)" killed two demonstrators and injured 150.
Source: Wikipedia — Athens Polytechnic March of 1980 (CC BY-SA 4.0)