Factual error: After the first victim they claim to have found a shell with 'Megan Turner' on it. That's not possible as we see Ron Silver fire at the victim and immediatley run away. If it had been an automatic then the gun would eject the shell, but it's a revolver, which doesn't eject shells.
Plot hole: Megan is suspended because the police were not able to find the gun the robber had (stolen from Eugene at the scene) and believed that she had killed an unarmed man. This is very unrealistic because surely they would have interviewed all of the hostages/witnesses at the robbery and each would have easily confirmed that the robber had a gun, and possibly that Eugene might have been missing right after the incident.