 Sobibor survivor Kurt Ticho, who had befriended Van Dam in the camp, later recalled that deputy camp commander "SS-Oberscharführer" (Staff Sergeant) Gustav Wagner had ordered Van Dam to paint him based on the image on a postcard.Ticho testified during the Sobibor trial in Hagen that van Dam had painted portraits for the SS.Another survivor, Ursula Stern, mentioned in her post-war statements that Heinrich Himmler had posed for a portrait by Van Dam on an inspection tour of the extermination camp and its gassing operations.