Since the central government could not control his activities, he continued to expand the area under his control and by 1922, cities of Baneh and Sardasht were under his administration.
In March, 1918, Mar Benyamin along with 150 of his bodyguards were assassinated by Simko Shikak (Ismail Agha Shikak), a Kurdish agha, in the town of Salmas (Persia) under a truce flag (see Assyrian Genocide).