The shotgun isn't kept in the ISS, it is stowed, unloaded, in the Soyuz up/down vehicle.
I would dare say 90% of weapons are kept the same way in America. In its storage box, unloaded, in the closet or a drawer.
What I find amusing out of all this is that russia and nasa have never exactly been rkba fans, they are also alarmingly weight conscious. Yet one sees the need to be ready "just in case" while the other lets it slide despite the non-pc nature of guns in space.