Gunshots break out when Tris and the Erudite reach the city.
On the way to the Erudite building, Fernando calls Tris an "Insurgent," defining it as "a person who acts in opposition to the established authority" (41.10). Hey, that's the title of this book. Tris likes the label.
Tris decides that it's time to get over her gun fear. She takes a gun from Christina and makes a break for Erudite headquarters.
Unfortunately, it's surrounded by Candor, who are under simulation to shoot on sight. They need to find another way in.
Tris and company decide to sneak into a nearby building and use their Windows. Oops, lowercase windows, as in glass on the side of a building, though Windows would probably be easier to break into.