When Grimmer shoots at Ellis behind the stained glass at Grand Central Station, his gun locks as if he has fired his last round of a magazine. When the camera comes back to him, the gun is back to ready position without his cycling a magazine.
Towards the end of the movie, at Grand Central Station, when Ellis shoots Grimmer, Grimmer is facing Ellis, and falls backwards through the glass. When the scene changes views to the terminal, Grimmer falls forward through the glass.
When Grimmer is shot, he begins to turn as he reaches the stained glass, so he WOULD fall forward through the glass.