The killings at Kent State

Updated 2:29 PM ET, Mon May 1, 2017
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Four students died and nine others were wounded on May 4, 1970, when members of the Ohio National Guard opened fire on students protesting the Vietnam War at Kent State University in Ohio. 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
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 fewer than two years earlier. Hulton Archive/Getty Images
On Friday, May 1, 1970, students at Kent State stage a protest on campus, the first in a series of protests. Kent State University News Service
A night of violence in downtown Kent is followed by a student march to the campus ROTC building the next day. Some students try to burn the building down. While the protesters claim they left the building intact and in the hands of campus police when they returned to their dorms, the building is destroyed. It is still not clear who burned it down. Kent State University News Service
The burning of the ROTC building brings 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 or feeling that violence would soon overtake the grounds. Kent State University News Service
Guardsmen patrol the area around the burned-down ROTC building. Kent State University News Service
The Ohio National Guard is called in to disperse a rally scheduled for at noon on May 4, 1970. Shortly after the protest began, guardsmen fired tear gas at the students. Some students said they were surprised the guardsmen followed them as they ran away from the tear gas. The guardsmen were clearly armed, but many students later said they believed their weapons were not loaded with actual ammunition. Kent State University News Service
A student throws a tear gas canister back at National Guardsmen. 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
Students run for cover after the National Guard opens 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. Howard Ruffner/Time & Life Pictures/Getty Images
Guardsmen patrol the empty Kent State University campus on May 6, 1970. The school was immediately closed and a strike involving more than 4 million students nationwide followed. ap