This very well could be murder, if they find any on line logs that state his intentions of harm. If by chance they do have him saying, I'm going to kill you ect....it can be concluded as pre-meditated, even though he was beaten and no weapon was used(that we know of).
Though the other individual showed \up to the fight, the degree of the crime is never based on the fact the guy should not have showed up, they simply look at the facts of the case determine if a crime has been committed and they go from there......but like someone said, its Russia, and they don't fuck around.......