Popper left school at the age of 16 and attended lectures in mathematics, physics, philosophy, psychology and the history of music as a guest student at the University of Vienna. In 1919, Popper became attracted by Marxism and subsequently joined the Association of Socialist School Students. He also became a member of the Social Democratic Workers' Party of Austria, which was at that time a party that fully adopted the Marxist ideology. After the <answer>street battle in the Hörlgasse</answer> on 15 June 1919, when police shot eight of his unarmed party comrades, he became disillusioned by what he saw to be the "pseudo-scientific" historical materialism of Marx, abandoned the ideology, and remained a supporter of social liberalism throughout his life.
What incident killed several of Poppers Marxist political comrades?
street battle in the Hörlgasse