It is just sitting there glaring at me, it doesn't do anything else. I can tell it would like to kill me. If I knew I could get a perfect replacement cat, I would kill this one now and replace it Friday afternoon. As we sit here glaring at each other I have already worked out several ways to kill it.
The simplest would be to drop heavy items on it from the upstairs bedroom though I have enough basic engineering knowledge to assume that I could build some form of 'spear like' projectile device from parts in the downstairs shed. If the atrium was waterproof, the most entertaining would be to flood it with water. It wouldn't have to be that deep, just deeper than the cat.
I don't know how long cats can swim but I doubt it would be for a whole week. If it kept the swimming up for too long I could always try dropping things on it as well. I have read that drowning is one of the most peaceful ways to die so really it would be a win win situation for me and the cat I think.