Members of the Student Afro-American Society (SAS), a black militant protest group, demonstrating on the Columbia University campus. On April 23, 1968, Columbia University students began a nonviolent occupation of campus buildings that lasted nearly a week. Students and community supporters called for the university to cut its ties to research for the war in Vietnam and to end construction of a gym in Morningside Park. Several hundred students gathered at the sundial on the Columbia campus led by the Student Afro-American Society (SAS) and Students for a Democratic Society (SDS). Some went to Morningside Park, where they tore down a fence around the gymnasium construction site and battled with police. Then they and other protesters marched into Hamilton Hall, Columbia's main undergraduate classroom building, occupied its lobby, and prevented the dean of the college from leaving his office. By morning, African-American students continued to occupy Hamilton, while other Columbia and Barnard students, mostly white, took over President Grayson Kirk's office in Low Library. After negotiations failed, the administration sent in the police, injuring many and arresting over 700, triggering a campus-wide strike that shut down the university.