Like any proper human who saw a sudden scary 'something' that appeared in their vision, one of their proper reactions was either to scream, punch it, or thwack it with something.
In Nagan's case, he performed the second option, as he swiftly hurled his prismic-black coated hand right at the top of the head like a whack-a-mole, to push back the cat-eared rogue vessel back to where he belonged. In a fashion that both didn't expect, the cat staggered and went limp for a second as if stars of confusion appeared above the feline's head.
"Ah, sorry about that."
In a wrathful, distorted voice, the cat replied with a voice filled with angst, "HOW DARE YOU THWACK ME LIKE A CHILDREN'S TOY!"