Four students were killed and nine were injured on May 4, 1970, when the Ohio National Guard fired on Kent State University students during a protest against the Vietnam War.

The event sparked a nationwide student strike that forced hundreds of colleges and universities to close.

President Richard Nixon addresses the nation in April 1970 to explain the expansion of the Vietnam War into Cambodia. Anti-war activists all over the country, including at Kent State, saw this as a betrayal by the President, who promised to end the war when he was elected less than two years earlier.
President Richard Nixon addresses the nation in April 1970 to explain the expansion of the Vietnam War into Cambodia. Anti-war activists all over the country, including at Kent State, saw this as a betrayal by the President, who promised to end the war when he was elected less than two years earlier.
National Archives/Getty Images
Students at Kent State staged their first campus protest on May 1, 1970.
Students at Kent State staged their first campus protest on May 1, 1970.
Kent State University News Service
A night of violence in downtown Kent was followed by a student march to the campus ROTC building the next day. Some students tried to burn the building down. While the protesters claimed they left the building intact and in the hands of campus police when they returned to their dorms, the building was destroyed. It's still not clear who burned it down.
A night of violence in downtown Kent was followed by a student march to the campus ROTC building the next day. Some students tried to burn the building down. While the protesters claimed they left the building intact and in the hands of campus police when they returned to their dorms, the building was destroyed. It's still not clear who burned it down.
Kent State University News Service
The burning of the ROTC building brought the Ohio National Guard to the campus. Some students described their presence as "frightening" and called it a military takeover. Others said the guardsmen were congenial and chatted with the students, with no sense that violence would soon overtake the grounds.
The burning of the ROTC building brought the Ohio National Guard to the campus. Some students described their presence as "frightening" and called it a military takeover. Others said the guardsmen were congenial and chatted with the students, with no sense that violence would soon overtake the grounds.
Kent State University News Service
Guardsmen patrol the area around the burned-down ROTC building.
Guardsmen patrol the area around the burned-down ROTC building.
Kent State University News Service
A student throws a tear-gas canister back at guardsmen during clashes on May 4, 1970. After several standoffs, the troops headed back up a hill in the direction of the ROTC building. As they reached the top, they turned toward the demonstrators and opened fire.
A student throws a tear-gas canister back at guardsmen during clashes on May 4, 1970. After several standoffs, the troops headed back up a hill in the direction of the ROTC building. As they reached the top, they turned toward the demonstrators and opened fire.
Popperfoto/Getty Images
In this Pulitzer Prize-winning photo, taken by Kent State photojournalism student John Filo, Mary Ann Vecchio can be seen screaming as she kneels by the body of a slain student.
In this Pulitzer Prize-winning photo, taken by Kent State photojournalism student John Filo, Mary Ann Vecchio can be seen screaming as she kneels by the body of a slain student.
John Filo/AP
Students run for cover after the National Guard opened fire. Twenty-eight guardsmen fired into the crowd for 13 seconds, wounding nine students and killing 4.
Students run for cover after the National Guard opened fire. Twenty-eight guardsmen fired into the crowd for 13 seconds, wounding nine students and killing 4.
Kent State University News Service
Kent State students gather around a wounded student.
Kent State students gather around a wounded student.
Howard Ruffner/Time & Life Pictures/Getty Images
Guardsmen patrol the empty Kent State campus on May 6, 1970. The school was immediately closed, and a nationwide strike followed that involved more than 4 million students.
Guardsmen patrol the empty Kent State campus on May 6, 1970. The school was immediately closed, and a nationwide strike followed that involved more than 4 million students.
AP