A flick and a growl

Dumb Cat is currently growling and flicking his tail in a very focused manner in the middle of the family room. Clearly he is hunting something. I am just very unclear what it is that he is hunting. And it makes me a bit nervous. After the mouse incident, and then the visiting cat hubbub, can you blame me? Now Lazy Cat is in on the action, but I am unclear on whether that is because she is curious as to what Dumb Cat sees, or whether I am missing the giant rabbit in the room somehow.