Too Mean To Keep?

A reader struggles with a dog who has become increasingly aggressive to other dogs, passers-by, and even family members.

I have a serious problem with my six-year-old neutered male Vizsla. He was a high strung, but good tempered dog for the first three years of his life. Something seemed to snap after that. He is loving and affectionate most of the time, but he gets aggressive when family members leave the kitchen (he and our other dog are limited to the kitchen and family room). He barks, snaps at them, and snags clothes with his teeth. He has never chomped down and bitten anyone, but he has scratched people with a tooth.