The gun that Moira Brown hired to guard her properties is notorious for his supposed restless nature, as he is never witnessed sleeping during store hours. He is a bit self-centered, judging by his gravely voice and the fact that he doesn't seem to like anyone. Regardless, this merc never questions his job of protecting the inventory of the Craterside Supply, and his very presence is enough to thwart shoplifters.
He stays out of the way of Moira's scientific pursuits, taking care that he has no business intervening in his employer's crazy experiments, since it's not part of his contract.
He doesn't seem to like anyone and talks in a gravely voice.
Due to his position and high chance of detecting the player, it is very difficult to successfully pickpocket him.
He seems to regenerate his supply of 5.56mm ammunition every day or so.
If the player character asks Confessor Cromwell about local gossip, he will tell you that Moira has hired a mercenary who "never sleeps". He does in fact sleep, however, just quite briefly and not until 5 AM.
Killing the mercenary may sometimes cause all of the citizens in Megaton to become hostile towards the player. They will remain hostile even after leaving Megaton and waiting for several days before entering again.