Originally Answered:
“There is a black animal with white feet hurting and attacking my cats at night and it always attacks my cats arm. Do you know any animal that would do that? The animal was the size of cat.”
Interesting. How is this animal getting into your house to attack you cats?
OK, I’ll stop being snippy, but this is one reason why you should KEEP YOUR CATS INDOORS! More wild animals and (especially) wild birds die from being attacked by domestic cats (house cats and feral cats) than from any other cause. Letting house cats roam freely outdoors is not good for the local wildlife, and (as you’ve experienced) it’s not good for the cats themselves. When outside, domestic cats are considered a non-native invasive species.
As to what’s attacking your cats, the first wild animal with white feet that comes to mind is a skunk. Racoons are another possibility (but they don't have white feet) and of course there are feral cats. Possums have white feet, but I doubt one would attack a cat.
[EDIT] This question is generating lots of comments and many are making similar points, so I thought I’d address them here…
- Cats have little impact on birds and other wildlife
The data shows that, by far, the largest cause of bird deaths is predation by domestic cats. Some studies have cited that domestic cats are responsible for the deaths of as many as three Billion birds annually: Cats and Birds | American Bird Conservancy (abcbirds.org)
- My cat only goes out briefly and my cat would never hurt a bird.
I can’t count the number of times I’ve had cat owners tell me essentially that same thing: “Oh! My Fluffy would never hurt a bird.” Well, these statements are not supported by the data. We may not see them do it, but it is absolutely clear that somebody’s “Fluffy” is killing a lot of birds.
- Keeping a cat indoors goes against their native instincts. They need freedom to roam.
I understand that as a pet towner, you want what’s best for your cats. I have also owned cats (but mostly dogs) and I understand wanting to give your cats the independence to roam freely and satisfy their natural instincts. The problem is that domestic cats are domesticated! Domestic cats are considered a non-native invasive species; they are not a part of the natural environment. Domestic cats are an introduced species—introduced by humans. Outside cats have not co-evolved in their environment. This is only one of many articles on this subject: Domestic cats an invasive species? The last biodiversity lecture of spring 2020 examines the issue (stetson.edu).
- My cat prefers to roam outside freely.
Wild birds prefer not to be eaten by your cat.
Finally, I understand that, for many cat owners, keeping your cats inside may seem callous, unhealthy, or even cruel; I know it’s not always an easy choice; but I want to make people aware of the impact their outside cats are having. We should keep our cats indoors and we should not encourage feral cats.
Some have mentioned neutering programs to control feral cats. These have worked with varying degrees of success, and they are a step in the right direction.
- тех у кого питомцы слоняются без присмотра. Не видеть/не слышать о проблеме можно только если не хотеть о ней слышать, и внушать себе что неожиданно пропавший котик не погиб, а его украли и он живет счастливо в новой семье 
Ну типа это рашка - где еще взять себе кота с расцветкой seal point кроме как своровать у соседа 
