A father and son drowned in the basement of their home. A young girl was killed when the storm surge swallowed her house. A woman was electrocuted when she stepped on a downed electrical line. Still others were missing: Two boys ripped from their mother’s arms by fierce waves, and a man believed to have been carried away by floodwaters. As authorities in nine states tallied the devastation brought by Superstorm Sandy and struggled to restore basic services early Thursday, the human toll mounted.