I have a five month old Bichon Frise. He's a complete sweetheart,
always friendly to every person he meets (usually TOO friendly) and
sees everyone as his best friend. The only time I've seen him bark
previously is when he sees his reflection in a full length mirror and
starts growling and barking.

However, I recently flew back to my parents' home with him for winter
vacation, and my puppy has become the most obnoxious barker. Everytime
someone walks through the garage door he begins incessantly barking,
and when my brother comes into my room in the morning to bring him
outside to go the bathroom, he begins growling and barking
fiercely--even though he knows him and has played with him. He even
tries to bite my brother. This has been going on for days now, and
nothing is helping. I don't know what's wrong with him. He's never been
this way, and it's really hard for me to see my sweet little puppy
turning into a biting, barking machine. He'll only calm down after I
pick him up and physically place him in the person's arms.

Do you have any tips on how I could help resolve this behavior? It's
driving me crazy. Any help you could give would be amazing.