Je vais tuer Hitler

One day, in Savigny, an 18-year-old boy left his house in the middle of the war, saying: "I'm leaving, I'm going to kill Hitler." His name was Joseph, he was Jewish, he was my great-uncle. He disappeared during the night of the Occupation, and his existence became a family secret. He disappeared from history, the small as well as the big: he is not on any deportation list, and the only archive where he appears is a family photo of him as a child. It disappeared like a stone at the bottom of the water, instead of going up in smoke in the sky of Poland. What did he become ? And why didn't anyone mention his name anymore?