Killian is the grandson of Junktown's founder, an American soldier who found himself without an allegiance after the nuclear holocaust devastated the planet. He is a tough, but fair, leader, aiming to make Junktown a safe and prosperous town for its citizens. He values law and order above all else, putting him at odds with the less reputable elements of the town's society, especially Gizmo, who resents Killian for "cramping" his business. Killian took over Junktown when his father died.
He wears his grandfather's dog tags around his neck, never parting with them.
"Well, there are two kinds, the Khans and the Vipers. We usually don't get trouble from the Vipers, and a few of them actually pass through town. The Khans, though, they're a mean bunch. They think they can conquer the world, or some such crap."
The random number of bottle caps in his inventory will reset any time you load a game or enter the area.
After you talk to him for the first time - when Kenji enters the building - Killian's inventory changes. The exact details vary, but he will always have a new Desert Eagle if you buy or steal the first one from him.
Killian's dog tags are lootable from his corpse whether or not Gizmo requested them for the proof of death.
Killian bears a very strong physical resemblance to his voice actor.
If you're caught picking any locks in the store, he will stop you. If you enter dialogue with him after that, you will be thrown in Junktown's jail.