Sounds like a fox squirrel, but without pictures, it would be hard to tell. We have them down here, but you can't hunt them any more, since so much of their habitat has been destroyed. That would be a Humongous squirrel, even for a fox squirrel. You have any nuclear plants, or waste dumps near you? Any meth labs near you?
Maybe you should take your pellet rifle, and trim his ......uh......that place in California,......uh oh yeah, el Ca hones
That might calm his aggressive nature down. My cat is a great squirrel catcher, and eater. But I don't know about a four pounder!
Heck, I would have to help him eat that one!
Yes, pictures......maybe even a video of the glass door confrontations......You might be a ten thousand dollar winner, on funniest animals.
Sounds like you have quite the entertaining squirrel there. Could he possibly be some exotic that someone let loose, or escaped?
Wayne