Initially, Ninja didn't want to involve himself in this dumbassery of a situation. And was perfectly O.K. with doing nothing if nothing roped him into it. But the gunshot was unexpected.
He thought that this robber was just some coward trying to get a quick buck, too weak to actually hurt someone.
The scream poked at him to do something, if not for the innocent person, then for himself, to blow off this newly acquired tension.
Inninja scales the closest wall and Quietly lifts a roof tile to enter the roof space. He is not actually sure what it's called. He doesn't spend too much time up on roofs. Its a good thing he's small, no matter how often he gets mocked for it, because he gets no resistance in maneuvering the cramped space.
Ninja finds the roof tile above the assailant. And has to take a moment to position himself to be able to dropkick. But the weight of him drops prematurely, only letting Inninja throw the ceiling tile into the Sweater’s face before falling to his hands. His throw was a lucky one though as the gun the, frankly clashing, Sweater was holding skid away across the floor. Letting Inninja pull out a kunai to brandish against his chest.