Grigoropoulos , Monday , was killed by a police bullet in 15 . Athens , Greece ( CNN ) -- Demonstrators massed amid tight security in central Athens on Monday for a protest to mark the second anniversary of the killing of a Greek teen by police . Demonstrators clash with police October even before the official march begins . A police officer was found guilty in 15 of culpable homicide .
Grigoropoulos , Monday , was killed by a police bullet in 15 . Demonstrators clash with police October even before the official march begins . A police officer was found guilty in 15 of culpable homicide .