Other mistake: When Mulder is on his knees in the cafeteria talking to the gunman, there are several shots where you can see the sides of his jacket hanging wide open because of his raised arms, which would make the gun on his belt easily visible to the gunman as he talks to him, but he somehow doesn't see it until he goes to take Mulder's phone.
Other mistake: In order to leave such bloody footprints, CSM must have stepped into the puddle of blood. It is impossible because the guy shot by CSM could not bleed so much blood in such short time, not mentioning that CSM must have intentionally stepped into it. (00:05:20)
Other mistake: On the information text at The Beginning of the scene telling the viewers where the scene is taking place, it is written as the "First Sovereign Bank of Pennslyvania" in "Harrisburg, Pennslyvania", instead of Pennsylvania, misspelling the name of the state both times.