Please help my dog with aggressive behavior!

Question
We have had our dog for a while now (maybe 2 months?) and he had never barked since we had gotten him. But about a week ago, he has started getting really aggressive with men. When my brother or my dad walks into the room, he starts furiously barking at them and growling. He gets down on the ground as if ready to pounce.

He is a 3 year old Yorkshire Terrier
He's only 7 pounds
But we need to stop this aggressive behavior it is getting worse and worse.

I am hoping this isn't a medical problem,
but he did have to be taken to the Emergency Vet Care for throwing up blood. But they said he was fine from what they saw. Just that he at something he shouldn't have and his stomach got irritated from throwing up so much and he started throwing up a little bit of blood.

Please help. My parents are threatening to give away the dog because he is getting more and more aggressive with my dad and my brother. We can't take him out on walks without him going crazy and barking at men who are outside.

Thank you VERY much
Anna

Answer
Anna, obedience training is a must. See if you can find a trainer in your area that can come to your house and work with you one-on-one with your dog. Without seeing him, it's difficult for me to give you advice, especially since this is aggression we are talking about. I would hate to tell you to try something and it result in someone being bitten. It's best to consult with a local trainer who has experience dealing with aggression.