How about six dead mice in the space of about three days? How about not finding whole mice, but finding just the back half? How about finding one of those halves in the washing machine as you are removing the clean clothes to the dryer?
My younger cat is doing his duty. After years of playing with toy mice, he has graduated up to real mice. (Though he did catch a mouse when he was only a couple of months old.) We think that the mice are coming in to avoid the constant wet outside after three weeks of rain.
We have found vomit with mouse parts. We have also found rear ends (tummy, feet, and tail). We haven't seen any heads or front legs. He must like those.