In the background of Amestris, a group called Blue Squad organizes itself to act against the Amestrisian government in acts of terrorism. Their leader had been captured prior to the events of the story. Bald and his associates hijack the civilian train carrying General Hakuro and his family to keep them as leverage for their affairs. When Hakuro protests, Bald reveals his immense automail arm and its gun by shooting off a big chunk of Hakuro's left ear.
The Elrics manage to subdue several of Bald's men aboard the train before they eventually come face-to-face with the terrorist himself. Edward and Bald do battle, noting that both bear automail arms though Bald's comes with guns and a secreted knife. Despite Bald's efforts, he is taken down and detained until the train arrives in East City. Roy Mustang appears to oversee Bald's capture, only for Bald to make an attempt on Mustang's life with his secreted blade. Mustang easily overwhelms the terrorist with his flame alchemy and sees that Bald is arrested. As a reward for taking down Bald, Edward and Alphonse are directed to Shou Tucker with the hopes of learning something to help restore their bodies.
In the 2003 anime, the events occur as in the manga with notable changes. Rather than being en route to East City, the event occurs as the Elrics are onboard the train heading to Central for the State Alchemist exams. They are aided by Maes Hughes in taking out Bald's men and the battle goes on as before. This time, it's shown that Mustang himself had set up the Elrics' presence aboard the train so that they would take down Bald and, by extension, impress Hakuro enough that he would recommend the Elrics for the exam despite the age limit.
Bald nor the event in question occurs in Brotherhood despite having been an event in the original manga.
Fullmetal Alchemist 2: Curse of the Crimson Elixir
Bald reappears in the second chapter of the game with his men, plotting to destroy the governmental outpost by attacking through the sewers. The Elric brothers defeat his associates and then take on Bald himself, who questions how some "brats" could have defeated him. Before he can attack, he is taken down by the arrival of Mustang who subdues the terrorist with his flame alchemy as in the manga. Bald is then presumably arrested as before.