Armen Sarkisyan, the founder of a separatist battalion fighting in eastern Ukraine, died after an explosion in an apartment complex, according to reports citing the Russian authorities.

Armen Sargsyan, the leader of a paramilitary unit wanted by Ukraine, died from his injuries following an explosion on Monday morning.

After an explosion in Moscow that killed the founder of a unit fighting on Russia’s side in the war against Ukraine, speculation swirled around two potential explanations: A turf war and a Ukrainian assassination.