Shamsudin (sun of the religion)? Could be sudden jihad syndrome.
You nailed it. Definitely Central Asian Muslim.
I wrote my M.A. thesis about the ethnic factor in the Russian military & decades later got deployed to Uzbekistan. Local Uzbeks seemed OK with Americans and they liked their vodka.
But our base camp was near the ancient city of Karshi where in 1916 there were horrific draft riots as the imperial army was running out of Russians to conscript and drafted Central Asians for the first time.
Muslims in Russia & their military will always be problematic.