In March 1945 he was arrested by the NKVD and taken to Moscow, where he was put on trial together with 15 other representatives of the Polish authorities. After three months of brutal interrogation and torture he was presented with the forged accusations of collaboration with Nazi Germany, sabotage, terrorism, planning a military alliance with Nazi Germany, owning a radio transmitter and several other trumped-up charges. He was sentenced to eight years in a Soviet prison and died there, probably murdered there on March 13, 1953, two weeks before the end of his sentence. His body was probably buried in the prison in Vladimir on Klyazma, though the whereabouts of his death, as well as the place of his burial remain classified.