What I find so interesting is that they appear to recognise each other as cats, despite the differences. I feel this is one more sign that cats are intelligent creatures. They're not even able to smell each other through the glass, at least I doubt it.
Or maybe it was just hungry. I've just looked up what it eats, and it will eat small dogs or a domestic cat. I suppose that's one more reason to keep your cat indoors if they are in your neighbourhood.
It looks a bit small compared to the pics I saw. A young one?