dog becomes vicous

Question
I have a soft coated wheaten terrier, he is about 6 years old. Usually his temperment is very mellow, he is gentle and a great dog. When he sees something outside or teh doorbell rings it's like there is a switch in his head and he becomes a completely different animal. Even if there is someone just walking past my house and i go to head towards the front door he will go to bite me. My mom has decided to have someone come in and look at him to find a home for him. I will be devastaded if they give him away. Especially not knowing who he is going to, and someone that won't use my vet. I'm scared someone might get frustrated with him, when he goes to bite them and they may hit him. Do you have any advice or anything I can do that can help improve his behavior in these sitautions. Pleast answer ASAP. thank you

Answer
Hi Erica,  How long has he been doing this?  Has he been obedience trained?  You can try spraying him with a spray bottle filled with water everytime he goes off.  At the same time, tell him "no" so that he understands that this behavior won't be tolerated.  Obedience training will help as you can have an upper hand on his attitude.  Hope this helps,

Dawn