On Wednesday night, I accidentally stepped on one of my cats, Simon, tail. He hissed at me, and then my other cat, Paulie, hissed at Simon. They hissed for a few minutes and jumped around the house and on tip of each other and went crazy and scared each other. I have been separating them like an someone suggested from Wednesday night to Sunday, but now I am letting them see each other with supervision. They have stare downs and hiss a lot. They both have been fixed and have gotten along great for 5 years. Anyone have any ideas?