A notch inside the big inscisor teeth is the diagnostic feature for House Mouse (if you still have the carcass). ID of small mammals from pictures is often uncertain but this looks like juv R rattus. Scale can help with photos of adults (<100 mm head and body for mouse).
Don, the photo was taken in 2011 and unfortunately I didn't put this one in my freezer. ;) Thanks for the tips for future rodent sightings. Cheers, Sandra