On February 17, 1988 the American Chief of the United Nations Truce Supervision Organization (UNTSO) observer mission in Lebanon, Lt. Col. William R. Higgins, was abducted and later killed after meeting with Amal's political leader of southern Lebanon. Amal responded by launching a campaign against Hezbollah in the south, It was believed that Hezbollah abducted him; Though the party to this day denies it and insists that it was done to create problems between them and the Amal movement.[6] In April 1988 Amal launched an all-out assault on Hezbollah positions in south Lebanon and the southern suburbs of Beirut. Early in May 1988 Hezbollah gained control of 80% of the Shi'ite suburbs of Beirut through well-timed assaults.