Cat attacked my dad, why? what should I do?

I left my cat with my dad while i was on vacation, and the first day the cat was there he escaped outside. My dad found him asleep on a car. The cat started squirming when he picked him up, at which point my dad grabbed him by the scruff of the neck. Then the cat began attacking my dad. He said the cat was startlingly agressive and bit my dad about 15 times before my dad was able to shake him off. This is very uncharacteristic behavior.

A bit of background. I live in a house with another cat, who is also a 2 year old neutered male. The other cat in very aggressive, and viciously attacks my cat, therefore they must be constantly separated. The few times that they have interacted with eachother the ensuing fights re frightening and completely one sided (the other cat is a bengal, and much stronger than my cat). Despite the situation, my cat has always seemed very calm and relaxed and I havent noticed any changes in his behavior. He is a very passive, relaxed, sociable cat. he likes being picked up, petted, and allows me to rub his belly. He is playful, he has never shown any behavior like this before.

I am wondering what I should do about this attack. I am taking this very seriously, because I cannot have a cat who may randomly attack. Could the aggression toward my dad have stemmed from the situation at my house with the other cat? Could it have been stress from being at my dads house? Could my cat have been angry cause he hadnt been outside in 4 months, and was mad that my dad wanted to capture him? Also, my dad said that the  aggression only started when he grabbed his neck, which makes me think he thought my dad was attacking him. Could this be an underlying aggressive streak that may not go away? Could he have some sort of medical condition? Im not sure what to do, i feel like I either need to move away from the bad cat situation at home, or put him down. Im going to make an appointment with a vet tomorrow, however I would appreciate any advice.

[Kimberly Coyner, D.V.M., DACVD]

From your description, it does not sound like this was a random attack; your cat was in a strange environment and was grabbed while sleeping, causing extreme fear and a defensive response. Since he has never acted this way before, as long as the same situation is not repeated, the biting behavior will likely not be repeated. There is no doubt that intercat agression can cause a cat to redirect aggression toward people in the household, but this usually happens right after a cat fight. To address all of your your concerns, it would be best to get the input from an animal behaviorist; one cat be found at http://www.animalbehavior.org/ABSAppliedBehavior/caab-directory.
Good luck,
Kimberly Coyner, DVM DACVD

[Suzanne Hetts, PhD]

Dr. Coyner is correct - this wasn't a random attack.  It's not uncommon for cats who get outside unexpectedly in an unfamiliar environment (and sometimes even in a familiar one)  to get "freaked out" and defensive.  Anyone who comes near (person, other cat, dog) can then be the target of a defensive redirected attack (meaning the cat is redirecting the behavior onto a target that didn't initially trigger the defensiveness).  It actually sounds as if your cat did a pretty good job of "holding it together" until your dad escalated things by scruffing the cat.  
Again, I agree with Dr. Coyner that this doesn't have anything to do with the relationship between your cats at home.
Once your cat is back in familiar surroundings, she should be fine.  However, don't be too surprised if she continues to display aggression to your dad if he tries to pick her up and/or handle or pet her.  The outside incident could have predisposed her to now expect "bad things" from your dad.  If you find that to be the case, then allow your cat to initiate interactions with your dad. Encourage that by having your dad entice her with dangling cat toys she can chase and play with, and/or by dropping tiny bits of some sort of irresistible food treat in a 'hansel and gretel" trail toward him.

It's always a good idea to get your cat re-checked by your veterinarian, but sometimes a trip to the vet is arousing and unsettling to cats which can produce the same sort of redirected response after they get home, so I'd put your cat in a quiet room for a couple hours.

[sbsarah84]

Thanks for the responses. Actually, he doesnt seem at all flustered by my dad, and after the incident has behaved totally normal around him (not to say that my dad hasnt been a bit distant). I took him to the vet today, and he was fine. and when i got home with him he sauntered out, and purred and came over to me for attention. so I dont think that the visit was an issue for him.
As far as the attack, my veterinarian thought that the outburst had a lot to do with my living situation, specifically the aggressive cat who is always prepared to attack and antagonizes my cat from behind a door all day.  intensified by the semi-new environment and my dads scruffing. I have decided to not bring the cat back to my house, since he is relaxed at my dads house and gets along well with the cats there.