I would run until I came up with a suitable plan, at which point, I'd try to put the plan into action. For instance, maybe I could get it to chase me across a bridge that's going across a bottomless pit, I leave a land mine on the bridge as I pass over it, and then when the monster passes over it, I never have to worry about it again. Or something like that. I sure as hell wouldn't stick in the place with the unstoppable beast, and while I don't want others to get hurt, I wouldn't shy away from getting some help either.