Altona Bloody Sunday (German: Altonaer Blutsonntag) was the name given to a violent confrontation between the Sturmabteilung (SA) and Schutzstaffel (SS), the police, and Communist Party (KPD) supporters on 17 July 1932 in Altona (Now in Hamburg, but at the time a part of Schleswig-Hosltein, which was part of Prussia). The riots left 18 people killed.

• http://en.wikipedia.org/wiki/Altona Bloody Sunday