JUBA: Gunmen in South Sudan opened fire on civilians  sheltering inside a United Nations base, residents and rebels said  Thursday, the latest atrocity in the war-torn nation. “They killed seven  people and injured 32, including a young boy whose father was also  killed,” said resident Jacob Nhial, speaking from inside the UN base in  Malakal in the northeast. Rebels also reported the shooting, but the  numbers killed could not be independently confirmed.