This week marks the 30th anniversary of the Greensboro Massacre. We need to recall it so something like it never happens again.

On the morning of Nov. 3, 1979, at the corner of Carver and Everitt streets in Greensboro, N.C., 40 Ku Klux Klansmen and American Nazis took out shotguns and automatic weapons from the trunks of their cars and opened fire on black, white and Latino anti-Klan demonstrators and union organizers who had gathered at Morningside Homes, a black housing project.

The KKK and Nazi members shot at anyone who wasn’t hiding while four television news teams and one police officer recorded the action. The murderers then got back into their cars and sped away, leaving five people dead and 11 wounded.

All five were members of the Workers Viewpoint Organization, and four of them were rank-and-file union leaders and organizers.

Let us remember the victims.

Sandi Smith was a nurse who’d been active in the black student movement and was trying to unionize textile workers. A black woman, she was shot between the eyes.

Dr. James “Jim” Waller, was vice president of the AFL-CIO local textile workers union. He led a strike in 1978 that helped the union grow from about 25 members to almost 200. He also had co-founded the Carolina Brown Lung Association.

Bill Sampson was a graduate student of the Harvard University School of Divinity.

Cesar Cauce was a Cuban immigrant who graduated from Duke University.

And Dr. Michael Nathan was chief of pediatrics at Lincoln Community Health Center in Durham, N.C., a clinic that helped children from low-income families.

When radicals began entering the mills, organizing cross-racially, and were elected to union positions, the power structure felt threatened.

The Workers Viewpoint Organization had a permit to rally that day. The group advocated antiracism, unionism and communist revolution. It advertised the event as a “Death to the Klan” protest.

Local police and federal law enforcement knew there might be trouble and did nothing.

Court proceedings later revealed that the Greensboro Police Department had an informant in the Klan to whom they had given a copy of the march permit and route, and who two days later would lead the white supremacist caravan. He informed for the FBI as well.

The federal Bureau of Alcohol, Tobacco and Firearms also had been running surveillance on the Workers Viewpoint Organization and had its own informant among the Nazis.

Sixteen people were arrested but only six were brought to trial. And though the murders were caught on camera, all-white juries acquitted the six defendants.

To this day, not a single gunman has spent a day in prison, although in 1985 a civil jury found the city, the KKK and the Nazis liable for violating the civil rights of one demonstrator. The city paid out $351,000.

Today, there is no historical marker at the site of the massacre, and the streets have since been rerouted and their names changed so the bloody intersection no longer even exists.

But we whitewash our own history at our peril.

Today, racist sentiment is on the rise, according to the Southern Poverty Law Center. Far right militia groups, incensed that there is a black man in the White House, are gaining recruits.

If we are not careful, and if we don’t remember our history and if the FBI and local law enforcement continue to infiltrate these groups and then lie low even as they take up arms, we could have more Greensboros in our future.

Kevin Alexander Gray is the author of the recently published books “Waiting for Lightning to Strike: The Fundamentals of Black Politics” and “The Decline of Black Politics: From Malcolm X to Barack Obama.” He can be reached at pmproj [at] progressive [dot] org.