A member of a bandit group who hijacked a train headed towards Central City so that he could trade the safety of the passengers on board - most notably General Haruko - for the freedom of his group's leader. Originally a member of the military, he desired an Automail arm to increase his power. This use of automail for unnecessary procedure was prohibited by the State, and Bald was discharged and became an outlaw, seeking revenge on the military that disbarred him. His automail arm includes two gun barrels and a small knife blade. While hijacking the train, Bald was confronted by Edward, who disabled his arm and defeated the bandits, an exploit which won him permission to take the State Alchemist entry exam. He would later resurface in "Curse of the Crimson Elixir" inside the sewers of Eastern City, and then "Stray Rondo" to repeat the same crime, only to be put in jail yet again both times by the Elrics.
In the manga, he's actually part of rebels who against Amestris, possibly from one of the southern bordering country which area had been taken by Amestris during the war.
In the anime, the event actually is part of a flashback to before Edward became a State Alchemist. Defeating Bald allows the Elrics to take the State Alchemist examination after a grateful Hakuro refers them. In the manga, Edward is already a State Alchemist (and fifteen years old) and returning from Lior. After defeating Bald, Mustang refers Edward to Shou Tucker and his research when Edward wonders if it would be possible to alchemically construct himself new limbs.