Help please my cavalier got aggressive

[Karen]

Until you seem to be in control and he's no longer displaying that aggression. Sometimes you may need to "review" it with him as well, but he will end up a happier dog anyway.

[Mazie]

With a dog that is resource guarding (which is what it sounds like yours is doing - guarding treats, food, toys, etc) don't just take the item away and then return it if he's good. Instead, trade the item for something better. For example, if you take the food bowl away, the dog gets a kong with peanutbutter as a trade. if you take away a toy, it gets a treat. This way the dog learns that when you take something, your not "stealing" his stuff, you are rewarding him for giving up what he has. When i did this with my dogs I also put a command to it. I simply say "trade" and the dog drops what is in his mouth and looks to me to see what he gets instead.