It's one of five hold ups in the city that investigators think the same person is responsible for, including a robbery at a St. Charles bank in April and one at a Palatine bank in May.
Agents have nicknamed the robber The Einstein Bandit because the equation "E= MC squared" is on the cap and jacket that was worn during several robberies.
Officials say the bandit did have a handgun during the hold-ups, but did not fire it.
Anyone with information should call the FBI at 312 421-6700.
