Naim Bey was the chief secretary of the Deportation Committee in Aleppo. "The Committee was charged by the Central Government of Turkey with the official responsibly of deporting via Aleppo the uprooted Armenians with the ultimate aim of exterminating them." 
After the arrival of the British at Aleppo, Naim Bey did not flee with the Turkish officials but remained back and in order to calm his deeply disturbed conscience handed to A. Andonian many official documents under his disposal received from the Central Government as regard the exterminations of the Armenians.
The Memoirs of Naim Bey was first published in London in 1920 with a introduction by Viscount Gladstone.
According to Naim Bey there were huge massacres after 1916: at Ras-ul-Ain, the present terminus of the Baghdad Railroad, where 70,000 were killed and at the aforementioned Der-el-Zor, where 200,000 Armenians were slaughtered. 
The Memoirs of Naim Bey
The documents provided in Naim Bey's memoirs are most damning evidence that put forward to support the claim of a genocide. Particularly incriminating are the telegrams of the wartime interior minister. If authentic, they provide proof that Talat Pasha gave explicit orders to kill all Turkish Armenians—men, women, and children.
One telegram dated September 16, 1915, notes that the Committee on Union and Progress had decided to destroy completely all the Armenians living in Turkey. Those who oppose this order and decision cannot remain on the official staff of the empire. An end must be put to their [the Armenians'] existence, however criminal the measure taken may be, and no regard must be paid to either age or sex nor to conscientious scruples. 
- The First Genocide of the 20th century by James Nazer, p. 63.
- The Lions of Marash: Personal Experiences with American Near East Relief, 1919-1922 - Page 15 by Stanley Elphinstone Kerr
- "Starving Armenians": America and the Armenian Genocide, 1915-1930 and After - Page 47 by Merrill D. Peterson
- Andonian, The Memoirs of Naim Bey, p. 64.