KEY WEST, Fla. — A 13-year-old boater was arrested Monday after authorities said he hit and killed a 6-year-old snorkeler, then sped away. The 6-year-old was snorkeling off Key West with his father and a sibling next to their 22-foot motorboat when he was struck, said Lt. Steve Acton of the Florida Fish and Wildlife Conservation Commission. An 18-foot skiff sped over the boy, then crashed into his father's vessel, causing it to sink. The driver paused momentarily before taking off, Acton said. Authorities found the skiff tied to a dock at a home and arrested the 13-year-old driver. He...