Symbolism, Imagery, Allegory
When zombies attack, gun control becomes a number one priority. And by gun control, we mean you better learn how to control a gun. Zombies don't exactly respond to pacifism. They only respond to getting their brains blown out. Guns represent protection and safety as well as death.
There are guns, from handguns to rifles, on practically every page of The Walking Dead. They're on the very first page, the very last page, and every page in between. When the zombies enter the picture, you better believe those guns are going to be fired. There are lots of BLAMs and even a PTANG or two as Rick teaches everyone to fire a gun by shooting at cans. The sound effects, in ALL CAP BLOCK LETTERS with an exclamation point convey the auditory sensation of gunshots.
One of the biggest human conflicts in the book is over a gun, namely whether or not Rick's seven-year-old son should be firing one. Lori says no, but no one else seems to have a problem with it. Carl's gun saves someone (Lori, when Carl shoots a zombie about to eat her) and leads to another's death (Shane, when Carl shoots him in the neck as Shane has his rifle pointed at Rick). We guess that evens things out, and it shows us both the risk and the benefit of a child knowing how to fire a gun.