Aggressive dog help
 

Fellow Menewshans who are dog owners! I need some assistance for a family member. I apologize ahead for the long post.

Here's some background:
My fiance's brother has a Chorkie (Chihuahua/Yorkshire Terrier mix) who is 5 years old, for the first 3 years of his life he has been the only dog until my future in-laws brought in a Cocker Spaniel, my fiance's brother got him when he was 8 weeks old, and the dog (Bane) is an alpha (because he was the only dog for so long).

Fiance's brother moved in with his girlfriend (who, in case this is helpful info, is expecting and due in Feb), and in this household that the dog is now in, has an established dog and cat.

Anyway, Bane has been aggressive and acting out towards people by biting and growling. He won't let anyone get near him and from what I gathered by her facebook post, he won't even let his "father" pet him or anything. I already posted something in a comment about what I think is happening (more background, I have known Bane since the day the brother brought him home at 8weeks and I know pretty much how this dog acts and am one of the few people he actually listened to- I am very consistent with reinforcement and training. I have cats at home and practice similar things on them and I carried over the dominance and consistency with the dog)

Here is my post that I left for her below.
What I am asking for is basically any tips or anything like that for dealing with an aggressive dog in this situation. I know I mentioned the whole thing of slowly integrating him (which they did not do... people seem to forget that).

If you know or can think of some things that could be helpful in this situation, find anything, or have been in this situation before yourself, let me know and I can send some stuff over to them if they would like me to. Thank you for your help in advance. :D

Oooh, that's not a fun thing to be going through... A lot of it probably is stress induced as well as being introduced to new animals so quickly. How long has he been in the new environment?

What I would probably recommend is similar to what you have, set up a place that is just for him. I wouldn't recommend a room just because he could get territorial over it. Perhaps a crate (or kennel, depending on what you want to call it)? Not to be used as a time out area, but if it's put somewhere safe and quiet, it could be 'his place'.

He probably just needs some time alone. They could try keeping him in a room for a few days (I know, going against the first thing, but this wouldn't be a forever thing). Keep him with some of this toys and familiar scents so he can get used to the new area. From there, you could introduce him to the others like we would with cats, set up a baby gate and keep him separate from the others but it would allow all parties to come up and sniff through the gate.

I hope one of those could work >.< Poor baby, he should hopefully calm in time. They just have to be patient with him and not lash out, that could enforce the behavior.