Weasels are such cute looking animals. If we could see into the minds of these playful and cuddly creatures, we would find little but thoughts of killing and killing some more. These are the happiest of psychopaths!
M nivalis but the Internet tells me there is also M frenata in Southern Canada.
Frontenac News tells me that mink are quite similar but larger than what I saw.
Encyclopedia of Life names 42 different species of mustelids.
Wikipedia has entries on Mustelids and on weasels.