[BoxerRescueMTL]

I HIGHLY suggest purchasing "The Culture Clash" by Jean Donaldson. She is the founder of and instructs at The San Francisco SPCA Academy for Dog Trainers, which has gained a reputation as the Harvard for dog trainers. You can order it on Amazon.ca and it'll get to your place very fast. It's an awesome book and it'll help you understand your dog and how he "works". And it's an easy read. She's also written a great book called "MINE! A Guide to Resource Guarding in Dogs" if it turns out that this is indeed what Joey doing.
Also, you should read about Calming Signals at http://www.turidrugaas.com There, you can learn how to interpret your dog's body language to see when he is stressed. This will help you tell when Joey is about to react, before it happens. You can also learn ways to calm him using your own body language. Turid Rugaas is a world renowned canine behaviourist.

Good luck! You can work through this