The evidence for this was accomplished via live-stream on Twitch.tv. The only actual name available is the player’s Twitch username, Fragnance. Eurogamer has also reported that Fragnance is still streaming the game, anxious to get his shadow priest up to level 110 as well. The character he used to reach level 110 with was the demon hunter, a newly introduced class from the last expansion pack. The name he used for the demon hunter was Sicklikeme.
Despite the game launching only yesterday, that hasn’t stopped this hardcore player from reaching a high max level. Time will only tell if other players will pass him or at least catch up to him.