Online events this week commemorated the 50th anniversary of National Guard troops killing four unarmed students at Kent State University and seriously wounding nine others during a protest against the Vietnam War and the guard’s presence on the Ohio campus.

Two years in the making, the activities had to be moved online, as part of the college’s adherence to social distancing orders. A live concert featuring musicians Joe Walsh and David Crosby, composer of Crosby, Stills, Nash and Young’s well-known anthem “Ohio,” was canceled.

Forced to forgo in-person events, university staffers were determined to make sure the fiftieth anniversary of the shootings was memorable. Online resources include a virtual candlelight vigil and a nearly hour-long video documentary released on May 4, the actual anniversary. Testimony from alumni is complemented with recorded commentary from current students who say what happened in 1970 has inspired them to work for social justice. David Crosby and other musicians known for their protest songs recorded video messages, which are also available on the school’s website.

Unable to travel to Ohio because of the pandemic, alumni in Massachusetts recalled their experiences. Bob Datz, a Cleveland native and current Worcester resident, was a freshman at Kent State in 1970. He said he wasn’t overtly political and planned to study criminal justice, or as it was called, “law enforcement.” But he vividly recalled the circumstances that led to the confrontation between students and the troops.

“A moronic governor called in the National Guard. His name was James Rhodes, and he was almost banging his shoe like (Nikita) Khrushchev except he was banging his fist,” Datz said, referring to a 1960 incident at the United Nations involving the former premier of the Soviet Union. “And he was saying that there was ‘this roving band of radicals going from campus to campus. And we're going to put a stop to it.’ So that fist pounding speech happened a couple days before the guard actually set foot in the town.”

The war in Vietnam was raging and campuses around the country were roiling with protests, especially after President Richard Nixon authorized the bombing of neutral Cambodia, Vietnam’s neighbor.

Datz remembered being more than a “curious bystander” as he walked through the parking lot near his dormitory. Two days earlier, students had burnt down the building housing the ROTC.

“At that point I was, you know, definitely against the war…you know the invasion of Cambodia, it happened. It was outrageous. And I was certainly ready to help express the outrage,” he said. “The troops were on campus…so I was ready to rally.”

The guardsman were using live ammunition. Tear gas cannisters were thrown back at them. But an FBI investigation found that the killing of four students was unnecessary and dismissed claims of self-defense by National Guard leadership as most likely fabricated.

Over the years, Kent officials have reached out to the guard to participate in commemorations such as the one this year. But Rod Flauhaus, a Kent State graduate and project manager who has overseen the fiftieth anniversary activities, told WGBH News the Ohio National Guard has declined.

“We would very much like to have a conversation with them. Not so much a debate but a real conversation,” he said.

For more than a year, the Kent State community has participated in panel discussions, conferences and concerts. Since mid-March, all events and resources have been online. Flauhaus recognizes that necessary adjustment has been difficult for people still processing their thoughts and emotions over the tragedy.

“Part of the healing process has been that coming together, to connect and share, and…give each other a hug, reconnect with people and have group conversations and discuss these things,” Flauhaus said.

Cancelling the physical commemoration was disappointing, he said, “not just for those who planned it, but obviously for those who wanted to come.”

On the other hand, he added, Kent State believes the school community will find the online resources meaningful as they reflect on the events of 1970 and civil turmoil today.

For Datz, 50 years has been a long time to reconcile how American democracy can live with a history that includes the shooting of unarmed students at Kent State and at Jackson State University in Mississippi a little more than a week later.

“The first lesson of the shooting itself is that this democracy will stop at nothing. Now, black people have known this for many more decades,” he said. “People living complacently don’t know it, and they will at some point know there are no limits to domestic tranquility and what’s necessary to maintain it.”

David Goodman is a production engineer and producer at WGBH News.