My cat is five years old, he's loveable, in my face, follows me, he's my buddy. I put both my cats and dogs in my garage when I go to work, it's very nice and warm. He started hissing at the other cat, went bisurk, chased her, then started to come after me. He was squalling, hissing loudly. I was actually afraid of him. He literally come after me, I had to grab something and put between us. I came home tonight, talked to him for about 30 seconds, then he went off again, looking at my other cat and started it again. I couldn't get near him, nor did I want to. I don't know why he's acting like that, both the cats have been together for over 2 years. They both are kept indoors all the time, never outside.