In 1987, Major Pierre Buyoya overthrew Col. Bagaza in a military coup d'état. He dissolved opposition parties, suspended the 1981 constitution, and instituted his ruling Military Committee for National Salvation (CSMN). During 1988, increasing tensions between the ruling Tutsis and the majority Hutus resulted in violent confrontations between the army, the Hutu opposition, and Tutsi hardliners. During this period, an estimated 150,000 people were killed, with tens of thousands of refugees fleeing to neighboring countries. Buyoya formed a commission to investigate the causes of the 1988 unrest and to develop a charter for democratic reform.