We found some information about Moritz Moshe Heller in the Memorial Book for the German Jews
In September 1944 he was transported from Westerbork to Theresienstadt and shortly after to Auschwitz. Many prisoners were transported from Auschwitz to Bergen-Belsen at the end of 1944 and the beginning of 1945 and he probably was among them. The 1st March 1945 was the official date he was declared dead.
Person is in the National Database of Victims of Persecution