Hard to believe then, hard to believe now. From Progress Ohio:
The Kent State shootings, also known as the May 4 massacre or Kent State massacre,occurred at Kent State University in the city of Kent, Ohio, and involved the shooting of students by members of the Ohio National Guard on Monday, May 4, 1970. Four students were killed and nine others were wounded, one of whom suffered permanent paralysis.
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. However, other students who were shot had merely been walking nearby or observing the protest from a distance.
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 eight million students, and the event further divided the country, at this already socially contentious time, along political lines.