A protester reacts as he kneels in front of a riot police officer during a demonstration in Athens on Sunday, Dec. 6, 2009. Protesters hurled rocks and burning garbage at police as violence erupted during a march to mark the first anniversary of the police shooting of a teenager, whose death sparked massive riots. Police fired tear gas at scores of hooded youths in central Athens, as several thousand demonstrators marched to commemorate the death of 15-year-old Alexandros Grigoropoulos.