I thought of another time this happened. One of my BIL's was living with us, and came home after a night of partying, forgot his key, and thought he'd jump the fence to come in through the back door (what, opening the gate was just too easy?). Anyway, when Jasper (GSD/Husky/Wolf) saw someone coming over the fence, he went into protector mode, barking, snarling and trying to bite him. We woke up, and turned on the light, and you could see it click on in Jas's brain "Oh, he lives here" and he was all over BIL wagging his tail and giving kisses.