On 11 July 1941 the Joodsche Weekblad published an obituary for Karl Marcel, drafted by his parents W. Cossmann and R. Cossmann-Huijsman and other relatives. According to the obituary, the death notice had been received from Germany. Karl Marcel Cosman was 18 when he died. The family lived at 112 Nicolaas Maesstraat in Amsterdam.
Het Joodsche Weekblad, 11 July 1941, 11