I hate to be the bearer of bad news, but your cat is, in fact, a vampire. Vampires are very adept at shape-shifting, and not all of them choose bat-form. Quite a few of them choose to be seemingly docile house cats, because they subconsciously crave the attention, plus they are capable of grooming in the sunlight in their cat-form.
You do have good reason to be worried, because his biting of the other cat suggests that he is turning his companion, bit by bit, and then you will have two vampire cats on your hands. That is a scary thing indeed, my friend, because when there are two, they are easily capable of forming intricate, diabolical plots to take you over while you’re sleeping.
Go to bed with a flask of holy water on your nightstand, a string of garlic around your neck, and a book of poetry by William Butler Yeats in your lap. If you awaken and see the cats sitting at the foot of your bed, staring steadily at you, immediately open the book of poetry and begin reading. For whatever reason, vampire cats love Yeats, and your reading of his work will lull them into complacency.
Once you have them subdued, shove a full tablespoon of peanut butter into each of their mouths. It will be so sticky that they won’t be able to bite you, and you will be safe long enough to finish your task. You must bury them in separate, silver boxes, precisely 27 feet apart. Surround each of the boxes with sea salt and peppermints. Shovel all the dirt into a giant cauldron and mix it well with five pounds of nutmeg. After it’s been well-mixed, dump the dirt back into the holes, burying the boxes.
Over each of the burial mounds, sprinkle lavender oil and plant a large Venus Flytrap, thus giving you peace of mind that if the vampire cats somehow get through everything else and reach the top, the lavender oil will burn their noses and paralyze their muscles, preventing them from running, and they will be eaten by a ravenous plant. I hope this information helps.