A good friend of mine, a noted film actor and director was vocally irritated by a peasant riding a burro across the scene my friend was filming. The peasant made the fatal mistake of yelling an insult to my friend and it was his last insult. The director pulled his pistol and killed the guy who was 70-80 yards away. He was jailed for a short stay, but an insult is an insult in Mexico.
Where did they buy the guns?
Not at the local gun shops, there are none.
I have a friend at work who is from Chihuahua (he's a citizen) that told me a story of his Grandfather. The old gentleman still rides out from his ranch on his horse carrying his pistol in his belt. He told me that his Grandmother makes sure the pistol is empty before he goes without his knowing it. The Federales leave him alone because he's so old and something of a local hero.