Other mistake: In the scene where Ecks is chasing Sever, you see Ecks put a shell into an open chambered shotgun. This means that there is only one shell in the gun. A moment later when he yells stop inside the building he cocks the gun again. Thus, he is holding up Sever without any shells in the gun.
Robert Gant: There are no innocent people in this world Sever, you know that. Only killers and victims.