I adopted a new cat a bit over a year ago now and he moved in with my other 7 year old cat just fine, but the other day he (the newer cat) was misbehaving and hissed at me, which caused my older cat (living with me since a kitten) to run and "defend" me and attack the newer cat.
Now she won't stop doing it. She's constantly on alert to sounds and movement and will harass and attack the newer cat on sight, bullying him into a hiding place then she will return to her bed or my lap and resume napping.
This has been going on for a few days now, she has a history of attacking other cats but there wasn't really a precedent that set that off like this event has. How can I get them to reconcile?