A 6-alarm arson fire tore through a large apartment building, including the apartment of a couple on the third floor who dropped their young grandson into the arms of a waiting firefighter, officials said. A man who came to a hospital with burns and claimed he started the fire was arrested, police said. Firefighters rescued at least 15 people, including the 6-year-old grandson of Herbert and Judith Lamb, who live on the third floor of the apartment building and said they were woken by an explosion and smoke.