At the time? It was just McCoy and Buffy there. Anyone else they'd had at the time were kidnapped, affected, or gone.

Buffy managed to fight the victim away from the vampire, but that left the matter of stopping him from bleeding to death while they waited for a proper healer to arrive. And it soon became very clear that this vampire was going to do everything it could to stop any help from coming, even if it just meant keeping the fight out on the front step.