Serene was a company town, owned entirely by the mining corporation, its houses, its stores, its streets. The Columbine mine sat on a rolling hillside, one of the few coal operations in Colorado that had not shut down during the 1927-1928 strike. For two weeks, strikers had conducted morning rallies outside the town's gates, asserting their rights in peaceful protest. The miners believed they had legitimate business in Serene. The town contained a public post office. Some of their children attended the school inside. But company towns operated by different rules, and on the morning of November 21, the miners would discover just how far those rules could be enforced.

The Colorado Rangers had been officially disbanded, but that morning they were recalled to duty. The miners arriving at the north gate were surprised to find men in civilian clothes blocking their path, armed with pistols, rifles, riot guns, and tear gas. Behind them, mine guards with rifles stood positioned on the mine dump, providing an elevated firing line. Scherf announced that the strikers would not be allowed to enter. For a few tense moments, the miners debated their options. "If you want to come in here, come ahead," one Ranger reportedly taunted, "but we'll carry you out." Strike leader Adam Bell stepped forward and put his hand on the gate, asking for it to be unlocked. A Ranger struck him with a club. A sixteen-year-old boy holding one of the American flags stood nearby. Someone snatched the banner from him, and in the struggle, the flagpole snapped across the fence.

What happened next remains contested. The state police later testified they had not used machine guns. The miners and some witnesses insisted machine guns had been fired into the crowd. Six strikers died. Dozens more were wounded. Some witnesses identified a mine guard who had climbed the tipple, the structure used for loading coal, and may have operated a machine gun mounted there. Others reported that one of Scherf's men operated a machine gun near a water tank. The discrepancy in testimony was never resolved. No one was ever prosecuted for the killings. The dead were buried, the strike eventually collapsed, and the Columbine Mine massacre faded from public memory.

Colorado remembers the Ludlow Massacre of 1914, when National Guard troops and company guards attacked a tent colony of striking miners, killing approximately twenty-one people including eleven children. That tragedy sparked national outrage and contributed to labor reforms. The Columbine Mine massacre, occurring thirteen years later, generated far less attention despite its clear echoes of Ludlow: unarmed workers, state forces defending corporate interests, deadly violence. Historian Leigh Campbell-Hale titled her 2023 book on the subject "Remembering Ludlow but Forgetting the Columbine." Today, little remains of Serene. The rolling hillside where the company town once stood has returned to Colorado grassland. A state historical marker notes the site, but the six men who died carrying American flags to a company town gate have largely been forgotten by all but labor historians.