A 3-day-old baby was fatally mauled by a pet dog in front of the child's parents at their Mira Mesa home Thursday night, San Diego police said Friday. The parents were in bed, watching TV, with their newborn son and pit bull-mix dog when the mother coughed, startling the dog, child abuse unit Sgt. Tu Nguyen said. The dog reacted by biting the baby, he said. The parents pulled the animal off and raced the child to a hospital, where he was declared dead.