I think we have all been thinking about this possibility, but have been cautious to admit it openly. It is time for an intervention.
Given the intermittent nature of the creatures habits, the obvious intelligence level of the quarry, and the inability of the OP to actually lay eyes on the animal himself....it is intuitively obvious to the most casual observer that what we have here is an unmistakable case of lycanthropy.
We are dealing with a wererat.
In fact the OP should come to grips with the fact that he himself could be the creature.
Only coming out at night, possibly during a full moon...........
sorry brother