This is by no means a complete list. It was actually quite hard to select the ones I wanted to include in the infographic which is limited to five as there are so many horrendous cat killers. These happen to be in the USA but there are others one of which is a pretty Asian woman who videoed the killing of her cat in her washing machine [link]. It has to be an allegation however because there is no hard proof except for the video. The five selected are all ‘proven’ although just 3 out of the 5 were found to have killed a cat or cats in a court through a deliberate action (Magnotta for instance) or due to gross neglect (Westberry). It focuses on domestic cats which is important as there is a very notorious lion killer living and working in America as a dentist in Minnesota, Walter Palmer [link]. He is off the list as lions are not domesticated.
There are many reasons for domestic cat killing. Some examples: to hurt a former spouse, because you hate cats, because you are a bird lover and you want to protect birds, because you seek notoriety, because you are mentally ill, because you are very angry and want to kill a person but can’t (yet),
Note: the selection was not based on the number of cats killed as you can see. It is based upon notoriety. A high-profile mass cat killer in the UK (now deceased because of cancer) was Steve Bouquet but he did not stick in my mind or there was less online activity around his crime than those that I have mentioned.
Below are some more articles on killing cats.