Who is the Pyro?

Interview with Demoman

Demo: HE'S A DEVIL! A BLOODY DEMON SENT FROM THE LOWEST CIRCLES OF HELL TO STEAL OUR SOULS! NO ONE BELIEVES ME, BUT I KNOW THE TRUTH!
Mr. Deep: Alright. Tell me, Demo, what is your reasoning for concluding that Pyro is a spawn of Satan?
Demo: He wields an unholy abomination that can control the bloody elements around him! And when he lights his victims ablaze, he cackles in a demonic tongue known only to his kin that dwell in purgatory.
Mr. Deep: Ah, yes. Well you see, his "abomination" is actually called a Flame Thrower. It appears to be homemade, but not forged by the weapon smiths of Hell. And his "cackles" are his mumbled words.
Demo: THAT IS A BLOODY LIE! You may not have seen that many demons in your time, lad, but I have, and Pyro, is one of the worst I've ever seen.
Mr. Deep: Do elaborate, if you'd please.
Demo: *takes a swig of his Scrumpy bottle* Ahhh. So...when I first met that...mumblin' menace, I was laying a trap of bombs near our cart. He did nothin' the entire time. Standin' there, starin' off into the wild blue yonder. But when the mission began, he changed. He ran ahead of everyone and with a swish of his "Flame Thrower", he had scorched the entire opposition to ash. He then laughed as the cinders blew off into the wind.
Mr. Deep: Well still, that doesn't qualify him of being a demon.
Demo: Ohhh... Think you so cleva do ya boyo? Think you're so smart because you have two eyeballs bouncin' in ya head?! WELL LETS SEE HOW SMART YA ARE WITH A BOMB SHOVED RIGHT UP YA BLOODY-*passes out*
Mr. Deep: The things I do out of curiosity...