Kat's thought about the vents when the topic came up. She really couldn't think of much that could have been making the noise. Maybe a few mole rats had gotten up there somehow but she really couldn't fathom why and how that would happen. Her only other explanation for it would be that someone had been making the noise on purpose. She remembered doing things like that back when she was a kid and frankly it was stupid back then and it is still stupids now. Her eyes followed Osaki as she slipped away from the group. She'd always felt sort of sorry for the girl. She'd heard her trying to explain that she was Japanese to people who had just assumed she was Chinese in the past. Kat had never really felt any type of prejudice to the standard of the refugees or Osaki for that matter. Of course, she had heard a comment here or two about her being vault-born in her past, but those were largely rid of after Kat's identity as a gang leader grew. To tell the truth, most of her reputation was just fabrication and myth. Word travels fast in the vault and it was like a giant game of chinese whispers so things Kat had gotten her cronies to do was attributed to her. 

Kat's head shot to the left as she heard the echo of gunfire. She looked back to the group quickly and frantically. Her hand flew up to her mouth and she began biting the corner of her thumb, cocking her head to actually be in the position to do that. She had never really used guns before, she had been taught how to use a pistol or two here or there when her father went to inspect security and the chief wanted to make a good impression on him. But other than that, guns were a scary, dangerous thing to her. Her speech was quick and frantic.
"What do you think that was? Is something happening down below?"