He can't be Death Gun, as both were present after Kirito's first fight.
Death gun's avatar is much taller too.
this weeks ep was extraordinarily boring, I didn't mind the part about Sinon and her friend, but pretty much everything else was so hard to endure and felt forced. The author tries so hard to make Kirito look like an antihero, but everyone knows that he will end up looking like mfing Jesus one episode later.