-OUCH...
GOOD THING YOU LOVE COOPER...GOOD THING YOU LOVE COOPER...GOOD THING YOU LOVE COOPER.
I worked in vet medicine for 25 years, and ran our rescue operations. I still do rescue at my home but on a much smaller scale. I've rescued/placed and trafficed many many dogs, cats and even horses over the years. Also, I've owned nothing but boxers since 1970 and all have been rescues. Some certainly take more work then others, but with patience AND TRAINING they have alll come around and are well behaved (while still retaining their silly exuberant nature) which is what I love about the breed. My father also raised and trained German Shorthairs for years.
A dog can get destructive for many many reasons unknown/UNANTICIPATED by you (especially youngsters). While it would seem unreasonable to us he may have experienced a surge of separation anxiety which can trigger highly destructive behavior. It made sense to Cooper at the time, but as the other person noted... there is a basket of toys right there. There are simply some negative behaviors you can't "love" a dog out of doing -especially since you don't know his history. If that's his first offense then maybe he just had a brain fart...but.. if he shows that to be a tendency I highly suggest you start with some crate training when leaving the room (yes...even if for 10 min). Was the den/office door closed or open? There is another method called "umbilical cord training", but if you're unsteady on your feet it might not work for you. I've used it with some rescues...and it worked well. It just keeps the dog very close in the early phase of training so you can correct any behaviors FAST before they launch into a disaster sans the couch cushion.
I never give a dog unsupervised house time until they show me reliable solid maturity - usually around 2-3 yrs old. I have seen soooo many disasters (mini-blinds torn to shreds, door knobs chewed off, furniture destroyed, sheet rock CHEWED off of walls, landscaping deeeeeestroyed, leather seats chewed off motorcycles - the list is about 100 miles long...LOL). Cooper is a powerful boy...and that mess may have just struck him as good clean fun... lol (oi-vey), but it could also be a sign of future things to come. When you first bring a dog home there is always what we call a "honeymoon" period where they are getting used to their new home and acclimatizing. Once the pet settles in their personalities and quirks can (and ususally do) come to the surface.
Go take a basic obedience class from a good trainer. If nothing else it will get Cooper thinking about being a better family member. It's a huge win win for both you and him.
Been there...seen this....LOL. It's fixable...but it will test your patience BIG TIME if this becomes a habit.
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I found this link on a quickie search. It will give you some tips that might help.
Umbilical Cord Training
http://www.dogtrainingbasics.com/PuppyControl.html
Even is Cooper is not a pup - if he missed his foundation blocks of training prior to you owning him he needs to be taken back to step ONE of puppy manners then training. If someone tells you crate training a dog is cruel they are 100% wrong. A dog is a den animal and if crating is done properly (and not abused) a dog is very happy there. My dogs are often sleeping in their crates with the doors wide open. I rarely close the crate doors, but when I do they are quiet and happy.