LAWRENCE, Mass. — Authorities are investigating the fatal shooting of a woman in Lawrence.Carrie Kimball Monahan, spokeswoman for the Essex district attorney, tells The Boston Globe that the woman was found with a gunshot wound inside a multi-family apartment building on Exchange Street at about 4 a.m. Saturday. She is believed to have been in her 40s.Monahan said the death is being treated as a homicide and there is no threat to the public.