I’d be more concerned about an author ruminating over all the different ways to murder children in his book than one that has been trained to use a firearm responsibility. Moreover, an author should at least be familiar with how guns function if they’re going to include them in a book.

Aside from the questionable combat tactics described in the novel, there is a scene where he describes a gun sliding back to reveal an empty chamber without a shot actually being fired. This would be impossible because it is the force of a bullet being fired that causes the recoil/slide action.