While Rex had yet to meet Mako, he knew one thing about the guy just from Korra's relation of events - that he was likely the reason the Avatar hadn't died. He'd had the guts to intervene and probably ended up doing a little fast talking to get them out of a bad situation, something Rex could respect.

"Well, at least now you know what a gun does, even if that's not much of a silver lining in all this." Rex leaned one elbow on the couch's arm rest, frown still firmly in place. "You should know there are a lot of different kinds out there, though, like just from my version of Earth alone. So if you think something might be a firearm? Probably better if you assume it is and don't let it get pointed in your direction."

He sighed and glanced away a moment, though when he looked back at her again, his expression and tone softened somewhat. "I'm really glad you're okay, though. If the worst had happened, well... I might have had to hunt this guy down and pound him into the ground. And you know how hard I hit."