Only theory police have so far is that man may have blamed doctor for bad teeth. A 56-year-old dentist was shot and killed Thursday on the sidewalk near his San Francisco office by one of his patients, who said only, "You remember me?" before opening fire, police and witnesses said. The gunman then crossed the street, got into his car, and shot and killed himself. Police investigators, relatives and co-workers of the dentist, David Gong of San Francisco, were at a loss to understand why the 44-year-old patient killed him. They said the gunman, identified as Hailu Abje of San...