@stux
He looks like he is defending his home and people. Our rescue takes defending my partner to ridiculous lengths. Fortunately, he treats me as a large but not so clever assistant for his job of "Guard Partner Against Evil And Especially From Dogs."
I can usually grab him while he's busy threatening some massive but bemused animal. Or delivery person. Or (once) a snake. Partner has to hang back/retreat or he'll just shrug and do whatever it takes to protect her..