That can't be good- spontaneous cat aggressiveness?

Maybe there was something wrong and the cat got mad... Did you let your cats outside anytime soon? Twilight might have been bit by and animal with rabbies and might have it. Make sure he does not bite you or scarch you and got to the emergency room with Stripes NOW. It might be too late for Stripes if it really is rabies. Then you will ahve tyo put both of them down if it is rabies...