Ukraine is marking four years since the liberation of Bucha, north of Kyiv, where Russian forces committed some of the worst atrocities of the war . Hundreds of civilians were found massacred across the city, although Russia continues to deny responsibility. Oleksandra Matviichuk, a human rights lawyer and head of the Ukrainian non-profit organization Center for Civil Liberties, which won the Nobel Peace Prize in 2022, tells DW that she was "shocked" by what she and her team discovered in Bucha