The family of Shaun Pinner, a British citizen captured by Russian forces while he fought alongside the Ukrainian military, says they are “devastated and saddened” by the death penalty handed down against him by a Russian proxy court. In a statement released by the U.K. Foreign Office, they said they believe Pinner should be considered a prisoner of war in accordance with the Geneva Convention. Pinner, 48, was captured in April while fending off Russian troops in the Ukrainian city of Mariupol. He had officially joined the Ukrainian Armed Forces prior to the Feb. 24 invasion, and had lived in Ukraine for several years. “We sincerely hope that all parties will co-operate urgently to ensure the safe release or exchange of Shaun,” the family said in a statement. “Our family including his son and Ukrainian wife, love and miss him so much and our hearts go out to all the families involved in this awful situation.” British Prime Minister Boris Johnson urged his ministers to take action Friday.