Guglielmo Tomasin was born on 25 September 1896 in San Vito al Torre (Udine) and lived in Ronchi dei Legionari at Via Brigata Modena 13.
He was arrested together with his son Valdi Tomasin following a denunciation during the roundup of 24 May 1944 and taken to the Coroneo prison in Trieste. After interrogation, he was put on transport no. 48, which departed on 31 May 1944 and arrived in Dachau on 2 June 1944 as a political deportee (red triangle). He passed through various camps—Allach, Blaichach, and Natzweiler—where he died on 9 May 1945.