It’s been 49 years since four students were murdered and nine more injured by bullets fired by Ohio National Guardsmen at Kent State University. The May 4, 1970 tragedy is one of those vivid moments in American history, both for its emotional toll and for the singularity of the act–American military firing on unarmed Americans.

The week before the students were shot and killed was tumultuous. Nerves were frayed razor thin and people were divided–both angry at and afraid of each other. On April 30th, President Nixon announced to a national television audience that a massive American-South Vietnamese troop surge was going into Cambodia, including heavy bombing. Nixon was elected in 1968 on a platform to end the war, and weary citizens were getting all too familiar with his words of assurance that “[w]e take these actions not for the purpose of expanding the war … but for ending the war and winning the just peace we all desire.”

The country had heard it all many times, but the desired end was nowhere in sight. For all the world, it looked like continued escalation. Kent State’s reaction to Nixon’s speech was similar to reactions on campuses across America. At noon on May 1 a group of about 500 history students protested by burying a copy of the Constitution, claiming that it had been murdered when U.S. troops went into Cambodia without a Congressional declaration.

Later that afternoon Black United Students held a rally for which they got permission before the Nixon announcement. About 400 came to hear the black students protest unwanted National Guard activity on campus. From there, word spread about a third protest, scheduled for noon on Monday, May 4 to protest the Cambodia invasion.

On the warm Friday night, the college scene turned into protest with students gathering in the nightspot filled “Strip” area of downtown. The crowd spilled into the streets with a spontaneous anti-war protest. Let’s say the students were not on their best behavior and the police decided to stay away after a barrage of bottles was hurled at them. Later, bonfires were set in the street.

On Saturday Kent State students were downtown cleaning up the debris from Friday night. Rumors began to spread that the ROTC building was a target for that night. The city of Kent was put on a dusk-to-dawn curfew and students were confined to campus. The mayor of Kent alerted the Ohio National Guard without informing the Kent State administration. Protests and confrontations between police and firefighters with student protestors ensued around the old, abandoned ROTC building, which was eventually burned.

On Sunday, the day before the massacre, National Guard troops had moved onto campus under orders from Governor James Rhodes. Rhodes was running for the Senate on a law-and-order platform and incited more unrest with a campaign speech in Kent that blamed the protests on “highly organized revolutionaries–the worst type of people.” He finished by saying, “we will use whatever force necessary to drive them out of Kent.” A Guard commander told his troops that Ohio law allowed them to shoot protesters if necessary, heightening the guardsmen’s hostility toward the students. Student action protesting the speech included a sit-in, which was tear gassed from helicopters.

On Monday, about 200 students gathered for the protest by 11:00 a.m. By noon the crowd grew to 1,500–some protestors–some spectators–none were “highly organized revolutionaries, the worst kind of people” wrongly described by Gov. Rhodes. The students were told to disburse–they did not. The Guard members marched toward students and fired tear gas into the crowd. Cannisters and stones were thrown back and forth between students and Guardsmen. The students retreated and the Guard seemed to be backing off. The incident looked under control and over.

Suddenly, on what was later deemed to be a verbal command from someone unidentified, 28 Guardsmen turned and in 13 seconds fired 67 rounds of live ammunition into the crowd of unarmed, mostly retreating students. Four students; Allison Krause, Jeffrey Miller, Sandra Scheuer, and William Schroeder, were killed and nine more students were injured, one suffering permanent paralysis. No one was ever convicted of a crime.

I write this review, not only to refresh our memories of an historic tragedy, but to send a message that we must learn from our history. The conditions at our southern border are not unlike the conditions at Kent State 49 years ago. The atmosphere of fear and that those wishing to seek asylum are “others” is similar to how the students and Guardsmen viewed each other with hate. Today National Guardsmen are at the border with loaded weapons watching over hordes of people. There have already been confrontations in which weapons were pointed at unarmed humans. So far so good, but there is no guarantee that the hate and fear will not suddenly spill into action and disaster.

My concern is escalated because of an incident at a rally Donald Trump was conducting recently. He queried about a solution to what could be done on the border and rally attendees responded with a loud “shoot them.” Mr. Trump could have bolstered confidence by showing leadership with a stern denouncement of that sentiment to his crowd, but he did not. He seemed to encourage the crowd’s solution with smiles and silence.

With an atmosphere like that, history is ripe to repeat itself.