Why are my resident cats fighting after a new kitten arrived?

Thank you for submitting your question regarding your cats. It sounds like your resident cat is stressed by the arrival of the new kitten. He is taking out this stress/anxiety out on your other resident cat. I would keep everyone separate for 24 hours. Then you can reintroduce your two resident cats. You will have to go slow with the kitten. Once your two original cats are used to each other again, continue introducing the kitten gradually. Wear clothing that you have held the kitten in and blankets the kitten has slept on to start. The introduce to kitten to one cat at a time. I hope this information helps!