Since you are in BC, I really suggest you post asking for HELP on the following BC rescue board. They are a wealth of information and I"m sure they can direct you to a behaviorist OR a trainer who deals with aggression issues.
BC Rescue board
In the meantime, here's a bunch of very good links on aggression you might want to look at.
Aggression
I hope you can resolve this, and I think you probably can, since your dog's aggression is situational and NOT genetic or a temperament problem!! He probably needs to be desensitized to strangers again.
Wearing the muzzle is not good, since if your dog ever bites again, the muzzle is proof that you knew he was dangerous.
Hope you can get the help you need. Please let us know!
