Montana too, IIRC.
Maybe they weren’t willing to count his garage as being part of his “occupied dwelling”. There is usually a real key locked, door to the outside style, door between your house and your attached garage.
People in CO shoot folks in their house (including drunks who are just in the wrong house) all the time without being subject to criminal or civil proceedings of any kind, but the garage has to make it at least a gray area.