This is a Sasanian-Persian soldier, probably a ranking officer (his upper body was protected by iron mail armour and he carried a sword with a pommel of jade, a semi-precious stone that can be tracked to Chinese Turkestan). He died a gruesome death in a claustrophobic tunnel below the walls of Dura-Europos in a fire that he may have intentionally set. His men were mining under Tower 19 (not far from the Palmyra Gate) when a Roman countermine broke through and enemy soldiers entered the tunnel.
What happened next is hotly contested.
In fact, it almost caused a diplomatic incident when Dr Simon James of the University of Leicester presented a new theory to an American archaeological congress in 2009. He argued that the soldier was a victim of 'friendly fire' as a poison gas attack against the Romans backfired on him.
From this one pic I can't tell if he died from poison gas, Romans hacking on his ass, or struck by fucking lighting. How did this almost cause and International incident.