"I know this question may seem silly, but is it possible to kill a demon?
If yes, is it possible with a gun?
And if these questions are silly, then i'd like to say i got the idea from the show, Blue Exorcist,"
that is just anime.. i love that anime thou.. hhmm.. if you want to kill a demon, go find the colt in the tv show supernatural.. lol.. just joking..
you can't kill a demon.. actually there are some who believe that angels and demons are just present within yourself and you just have to harness it within yourself and some do believe they do exist.. and about killing it, just put this in your mind you don't exactly know what a demon is so why do you want to kill it? (yes i know that those ideas about the demon is just what your old ones have told you since birth).. a demon is a higher being, a divine in nature and they really are teachers in many arts..
if you want to know about demons, put aside your judeo-christian beliefs and explore the said dark side of magick.. (and about the dark side doesn't mean it is bad, just negative.. not evil)..