In 1941 Marek was drafted to a military work unit in Slovakia. In December 1943 he moved to Hungary, was caught and detained in the Tolonc prison. He escaped and joined the underground activities. Marek saved the lives of members of the movement and other Jews. Thanks to his Aryan appearance he was able to move around freely in the streets of Budapest while wearing an Arrow Cross uniform. On his way to deliver forged documents, in December 1944, he was caught by Arrow Cross men and executed.
