 Walter Gerhard Martin Sommer was an SS-"Hauptscharführer" who served as a guard at the concentration camps of Dachau and Buchenwald.Known as the "Hangman of Buchenwald", he was considered a depraved sadist who reportedly ordered Otto Neururer and Mathias Spannlang, two Austrian priests, to be crucified upside-down.Sommer was especially infamous for hanging prisoners off of trees from their wrists, which had been tied behind their backs (a torture technique known as strappado) in the "singing forest", so named because of the screams which emanated from this wooded area.