Kent State shootings
The Kent State shootings—also known as the May 4 massacre or Kent State massacre<2><3><4>—occurred at Kent State University in the city of Kent, Ohio, and involved the shooting of unarmed college students by members of the Ohio National Guard on Monday, May 4, 1970. The guardsmen fired 67 rounds over a period of 13 seconds, killing four students and wounding nine others, one of whom suffered permanent paralysis.<5>
Some of the students who were shot had been protesting against the American invasion of Cambodia, which President Richard Nixon announced in a television address on April 30. Other students who were shot had been walking nearby or observing the protest from a distance.<6><7>
There was a significant national response to the shootings: hundreds of universities, colleges, and high schools closed throughout the United States due to a student strike of four million<8> students, and the event further affected the public opinion—at an already socially contentious time—over the role of the United States in the Vietnam War.<9>
Historical background
Richard Nixon had been elected President in 1968, promising to end the Vietnam War. In November 1969, the My Lai Massacre was exposed, prompting widespread outrage around the world and leading to increased public opposition to the war. In addition, the following month saw the first draft lottery instituted since World War II. The war had appeared to be winding down throughout 1969, so the new invasion of Cambodia angered those who believed it only exacerbated the conflict. Many young people, including college students and teachers, were concerned about being drafted to fight in a war that they strongly opposed. The expansion of that war into another country appeared to them to have increased that risk, although the number of troops serving in Vietnam had peaked in 1967, well before that time. Across the country, campuses erupted in protests in what Time called "a nation-wide student strike", setting the stage for the events of early May 1970.
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http://en.wikipedia.org/wiki/Kent_State_shootings