A 6 year-old boy was found dead yesterday morning, his hands and ankles bound and a gag stuffed in his mouth, in a water-filled bathtub in his Southesast Washington apartment, authorities said.The boy appeared to have been dead for hours, perhaps longer, police said. He was alone in the apartment when his grandmother found him at 8:15AM, facedown in about a foot and a half of water, they said. The grandmother, who had come by to pick him up for summer camp, called 911 and was "hysterical" when police arrived, authorities said.Police said that the cuase of the boy's death...