Searching for a Bank Heist Movie from between the early 2000s and early 2010s. The Plot twist is, that there is a serial murder in the Bank

Looking for an American indie film from the early 2000s-2010s. Bank robbery, robbers take hostages inside a small bank outside a city. One of the hostages turns out to be a serial killer and kills everyone one by one, including the robbers. The bank manager is either the killer or gets killed. Watched on DVD. It is NOT The Last Heist.