In August 1991, internal dissent among the rebels led opponents of Garang's leadership, most importantly Riek Machar and Lam Akol, to attempt a coup against him. It failed, and the dissidents split off to form their own SPLA faction, the SPLA-Nasir. On 15 November 1991, Machar's SPLA-Nasir alongside the Nuer White Army carried out the Bor massacre, killing an estimated 2000 Dinka civilians. In September 1992, William Nyuon Bany formed a second rebel faction, and in February 1993, Kerubino Kwanyin Bol formed a third rebel faction. On 5 April 1993, the three dissident rebel factions announced a coalition of their groups called SPLA United at a press conference in Nairobi, Kenya.