Dr. Martin Niepage was a senior teacher at the German Technical School in Aleppo (other sources speak of the German Realschule in Aleppo).
His report appeared under the title: Ein Wort an die berufenen Vertreter des deutschen Volkes - Berlin, Der Reichsbote 1916 (as a "confidential report").
The quotation to which I refer with my work "Armenian Hands" see p. 12 of Niepage's text "THE HORRORS OF ALEPPO"
In case you read German, you find more info about Dr. Niepage and Dr. Graeter at bottom of the German version of his text.
The three photos of Consul Hoffmann (Hermann Hoffmann-Fölkersamb) mentioned in Niepage's text on bottom of p.9.
Source: Photo archive of the Information and Documentation Center Armenia (Fotoarchiv des Informations- und Dokumentationszentrums Armenien, Berlin)
Originals in the Political Archive of the German Foreign Office (Politisches Archiv des Deutschen Auswärtigen Amtes PA/AA)
Thanks to the source: https://archive.org/details/horrorsofaleppos00niep/page/6/mode/2up?view=theater
The three photos are supplemented by me.
This report Niepages was obviously very significant:
"Martin Niepage wrote an account of his experiences in Aleppo entitled The Horrors of Aleppo. Niepage was later sentenced to death in absentia by the Turkish government for publishing the account."
Footnote 136:Goçek, Fatma Müge; Naimark, Norman M. (2011). Suny, Ronald Grigor (ed.). A question of genocide Armenians and Turks at the end of the Ottoman Empire. Oxford: Oxford University Press. p. 214. ISBN 978-0-19-978104-1.