In January 2015, Gashi left Germany to join up with Islamic State militants in Syria. To cover his whereabouts, he claimed he was headed to Thailand on a sports mission. He was married and had two children and left them behind when he joined the extremists. He later revealed that he had joined ISIS and was helping in patrolling in the Manbij area and the Euphrates River near the Syrian-Turkish border looking for smugglers trading in cigarettes, alcohol and drugs, all forbidden in ISIS-controlled areas. His father Enver Gashi pleaded with him through the media to return to his family, but to no avail. In a later interview with the Swiss German SRF station in June 2015, he said he was "trying to help build a modern caliphate in Syria" adding: "If I die while doing good, I of course will be glad." His death was widely reported on 6 July 2015 after his brother confirmed the death of Valdet on 4 July.