Joe Lewis was just 18 when he was shot twice by the Ohio National Guard on his college campus.

A freshman at Kent State University in Ohio, Lewis had saved money working at the post office during high school to pay for his first year of college. He loved the freedom college afforded, and in 1970, the campus was abuzz with the “excitement of being on the cusp of a new world,” he said.

Lewis grew up on images of the civil rights protests and the Vietnam War, and took part in anti-war protests when he got to the campus.

But in May, things escalated and then turned tragic.

Vehemently opposed to President Richard Nixon’s escalation of the war into Cambodia, students at Kent State began protesting. On Friday, May 1, students demonstrated on campus and throughout the town of Kent. The next day, the Reserve Officers’ Training Corps building on campus was set on fire — how the blaze started remains up for debate — and by the evening, then-Gov.Jim Rhodes, who was running for the Senate, called in the National Guard. That Sunday, in a press conference, the governor called the students “the worst type of people that we harbor in America.”

By Monday, May 4, things reached a boiling point, and students weren’t just protesting the war anymore, but also the armed guards stationed on their campus with military-grade weapons. Lewis was among the estimated 2,000 people who gathered that afternoon in a demonstration beset by the “toxic waters of the 60s flowing together in one place,” according to historian Howard Means, who wrote a book on the incident, “67 Shots: Kent State and the End of American Innocence.”

“You had this combination of naive students, a politically ambitious governor, and a laissez-faire administration all deeply complicated by terrible leadership in the National Guard,” Means said. As the National Guard ordered Lewis and his fellow students to disperse, they refused. The guardsmen used tear gas, but it proved largely useless due to the wind, and students threw rocks. While this was all happening, the important school administrators were out to lunch, Means said.

Then, the guardsmen, at least 60 yards from most of the students protesting, started firing. In 13 seconds, between 61 to 67 shots were fired. Lewis was hit twice, four students were killed, eight others were injured, one of whom was permanently paralyzed, and the course of history was altered.

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“I remember stopping, and there was absolute stillness,” Lewis said of the moments after the shots. “Then, screaming and wailing and chaos. I didn’t lose consciousness, I was in a state of shock.”

Kent State University student Joe Cullum (center, with beard) and others kneel on the grass beside wounded fellow student John Clearly after the latter had been shot when the Ohio National Guard opened fire on antiwar protesters in Kent, Ohio, on May 4, 1970.Howard Ruffner / Getty Images

Many details about the tragedy remain unknown, even today. Why exactly did the guardsmen start shooting? Were the guardsmen who later claimed they feared for their lives telling the truth when there was so much space between them and the students?

What is known is that in the immediate aftermath, public opinion largely sided with the National Guard, but the shooting accelerated the growing disapproval of the Vietnam War.

“It was definitely understood very quickly as an indication that things in the U.S. — on and off campus — were spiraling out of control,” said Angus Johnston, a historian on student activism who teaches at the City University of New York.

Johnston called the Kent State shooting “a turning point in American history” for this reason. The report Nixon commissioned on campus unrest after it said that “a nation driven to use the weapons of war upon its youth is a nation on the edge of chaos” — and Americans were feeling that “chaos.”

Days after the Kent State shooting, on May 15, there was the shooting at the historically black Jackson State College in Mississippi during a protest against racism that students on campus were facing. Two students were shot and killed and 12 were injured at the hands of the police.

Rioting students run through tear gas at Kent State University in Kent, Ohio on May 4, 1970.AP

Society was “spiraling out of control,” Johnston said, in a war it wasn’t winning and shooting its own students dead. Although the May tragedies certainly weren’t the only time campuses saw violence, the dramatic photos of the Kent State shooting revealed to the American public what was really going on. The deaths of the students in Ohio (which received far more attention than those in Mississippi in part, historians believe, because the students who died at Kent State were white), not only further divided a country already split over the war but also revealed that the divide was growing unsustainable.

Alan Canfora, a student who attended the Kent State protest, said the purpose of the demonstration — one that he never imagined would turn deadly — was “to send a message to stop the war.” Canfora was captured in one of the most famous pictures from the day, holding a black flag while facing down the National Guard. He was holding the flag in mourning — one of his close friends from childhood had died in the war. Just a week before the protest, he had attended a funeral of someone else he knew who died in Vietnam.

Means, the historian, said he believes that the message of Canfora and his fellow students was received. Kent State, he said, “unmoored Nixon,” who just days before the shooting had called anti-war protesters “bums,” to which a parent of one of the students killed that day famously replied, “My child was not a bum.”

When the president’s intelligence officials couldn’t find evidence that the protest was stirred by outside agitators, Nixon was frustrated. The anger was coming from the students themselves — and it was only growing.

Ohio National Guard move in on rioting students at Kent State University in Kent, Ohio on May 4, 1970.AP

After the shooting, there was a nationwide student strike that saw 4 million turn out in response to the tragedy. As many as 100,000 students marched on Washington. Then, David Crosby, Stephen Stills, Graham Nash and Neil Young released their protest song “Ohio” a month later, with the chorus of “four dead in Ohio,” after seeing the photos of the shooting. With lyrics that directly called out Nixon, the song was heard by the nation loud and clear.

A year after Kent State, the 26th Amendment was ratified, lowering the voting age to 18, which was seen as a massive win for students who until then were too young to vote for politicians who wanted to end the war but were old enough to be drafted.

Canfora, who was shot in the wrist that day 50 years ago and returns to the campus every year to mark the anniversary, is proud to have been there despite the tragedy.

“We helped stop the war,” he said.