04 May 1970,
Four students were shot dead by the U.S. National Guard at Kent State University in Ohio. It was in the context of protests against the Vietnam war. On 1 May, thousands of young people mobilized against the measures announced by Nixon and there were incidents in many places with the police. The great protest, called on 4 May, was banned by the authorities, but thousands of young people mobilized and the National Guard violently confronted them. The deaths were called Allison Krause, Jefrrey Miller, Sandre Scheuer and William Schroeder.
Source:
Mrs. Carole A. Barbato, Laura L. Davis and Mark F. Seeman, This We Know. A Chronology of the Shootings at Kent State, May 1970 (The Kent State University Press).