Cat attacked my dog

My cat Reagan attacked my pitt (chito) today, scratching him leaving pieces of his nails in head, ear, and hind end for no apparrent reason. Had Chito retalliated you would probably hear a story about another pitt bull attack. This is not the case. Reagan came into our home at 2 weeks, his mother was hit by a car, he is not 4 1/2 yrs and chito is 6. Chito basically raised Reagan from day 1 and the 2 have been unseperateable from the beginning. Several mos ago I started noticing Reagan picking on Chito whenever he was asleep. He would sneakup on the bed and scratch his face or some part of his body. Today was the ultimate attack, he jumped on him and chased him around the house and even when i got Chito into the room Reagan still tried to get in to continue the fight until I locked him up in the bedroom for a while. Does anyone know what would cause this behavior. I'm not so sure I want to leave the house and leave them alone, I do have 3 other cats and another dog, as well as birds, and a hamster, but Reagan dosen't seem interested in them, only in Chito. Any advice would be helpful.

Wow... I have never heard such a thing, most dogs would not stand for that, and would fight back... I would fight back! lol
   
Anyway to try to help... not that I am experienced with cats at all, but here goes my advice...
   
It seems that Reagan seems to think he can boss Chito around, and gets away with it. He is either trying to take control, or has some underlying problem... and is taking it out on Chito because he knows he will get away with it, where the others would fight back?
   
Anyway you need to take charge and let him know he cannot do that, any time you see any bulling at any level not just the aggression I suggest giving Reagan a firm no and shutting him out of the room...
   
I would also recommend watching the pack together and see if you can notice any body language to see any other bullying, and sort that out. Has Reagan seen a vet recently/has any other problems?

Reagans is being a bully and I don't know why. Something is going on, when we go out we put a pad down for the dog to use incase we don't get back home in time to let him out and by golly Reagan is using it now and he is still dogging Chito, however today I noticed that he started to dog him, when Chloe my little cocker/toy poodle came out of the room and growled and stared him down then he ran off to the kitchen to hide under the table. Chloe seems to know that Reagan is giving Chito a bad time, also they used to sleep together on my daughters Cal King bed and now Reagan will not let Chito get on the bed. He will do everything in his power to keep him off, he's afraid of Chloe but not of Chito and it dosen't make any sense. Meanwhile Chito hides behind Chloe and they say pitts are aggressive, but they haven't met our pitt yet. I took Reagan to the vet just to be on the safe side and doc gave the A-OK healthwise, but attitude wise he says don't let him get away with it. I seem to have a problem