What Can I Do About My Dogs Recent Aggressive Behavior?

Any dog will try and change their status in the pack you're going to have to be really stern with this dog, no messing around, you are the leader of the pack and let him know that on every occasion. Or yes he will bite someone. He's decided to make his move, and you've got to decide he's not getting to get away with it. This is a clear case of a dog, making his move in the pack hierachy, I went and found exactly what you need to do, and you need to begin promptly. Notice the order in which all actions are taken. The first source is the one you need. Good Luck.