Maybe it's because he's tired. Maybe it's because he's aching and completely worn out from a long, nasty hunt that ended in an even nastier fight. Maybe it's because his left arm feels like it's been stuck through with hot pokers, aching bad enough that just about now he wants to cut the damn thing off rather than deal with the pain any longer (definitely broken, possibly even bad enough to require surgery, god damn it). Maybe he's distracted, still thinking about the beautiful young nurse with the blond curls whose eyes sparkled daringly as she told him he was the handsomest fed she'd ever brought in to look at half-eaten bodies.
Maybe it's the pathetic keening noise they're making as they stare up at him with their dark, liquid eyes, too young to shape-shift still and so stuck in their pitiful original forms. And yes, maybe they remind him just a little of two other shy-yet-defiant young things he left in a motel, the way the younger one is pressed into the older, the older staring boldly back at him even as both tremble in terror…
It doesn't matter why. What matters is what John Winchester does, which is raise a hand to stop Joe as he raises his gun to finish off the tiny fledgling ghouls.
"Ghouls're bottom feeders," is the reason John gives. "That one—" A vague gesture to the headless corpse at the foot of one of the crypts—"Probably never woulda killed if he hadn't been interrupted while feeding. If they survive, these two'll probably never even learn to like human flesh."
Joe shrugs. "You're the expert."
John wants to laugh at that.
"You killed him."
Both of them jump when one of the ghoul pups speaks; John hadn't reckoned they were old enough to talk just yet.
"You—he's dead."
"Name's John Winchester," John tosses off, because what the hell. "Look me up in a coupla years."