When I was 6 years old, I read a Judge Dredd comic where a criminal tried to use a lawgiver (Dredds gun) on Dredd, and got his ass handed to him because it was gene locked... Doesn't the lawgiver electrocute unathorized users in the old movie?
At about the same point in my life I heard exposition about an exploding 6 year old on M*A*S*H* taking out a squad of marines.
And honestly what idiot doesn't know what the tracking function to that gun looks/feels like? He's an idiot, ignorant or he knew he was leading kiera back to his buddies.
It's not secret technology.
It would be like some one in the modern day thinking that a cops pepper spray is airfreshener or their their nightswtick is a half a set of chopsticks.