Apparently, NPCs hate me. Not only do they kill me now, they also give me errors when they run out of ammo. Just spawn a bunch of things around an armed NPC and he too will (probably) give you errors. Also, if you die or create a new char whilst the bullet-less NPC is still alive, his errors (and himself for some strange reason) will come greet your new character every few turns as well.
Because he can’t reload. And further testing showed him successfully reloading uselessly every turn, even though the ‘Can’t Reload’ error still comes up. A screenshot is below, along with a savefile of the first time this error occurred.
PS: The error started coming up when he killed a bear and ran out of ammo whilst doing so.