There have so far been more mass shootings in the U.S. in 2019 than days of the year. According to the Gun Violence Archive (GVA), there were 381 mass shootings as of November 29, the 333rd day of the year. While the Federal Bureau of Investigation (FBI) doesn’t have a formal definition for mass shooting, the GVA defines it as any incident in which four or more people are shot or killed at one time, not counting the shooter.

These acts of carnage and bloodshed have traumatized so many, leaving us second-guessing about whether it’s safe to venture out into open public spaces.

But while school administrators, psychologists, and politicians have their own theories for what’s behind the violence, there’s also one crucial detail that’s regularly left out of the conversation: The fact that the United States has a long, bloody history of mass shootings. The truth of the matter is this country was founded on colonial violence — built on the backs of black slaves and the bodies of millions of slain Native peoples.

David Hogg, a survivor of the February 2018 Parkland mass shooting and one of the cofounders of March for Our Lives, acknowledged this reality during a recent interview with MSNBC host Chris Hayes. “If we want to talk about mass shootings, we have to recognize the massive number of Indigenous mass shootings that were committed by the United States government,” he said.

The history of America is one of brutal mass slaughter, dating from the genocide of this land’s original peoples to the shootings we see in shopping malls and schools today.

November 29 is the anniversary of the Sand Creek Massacre. On that day in 1864, U.S. Colonel John Chivington led around 700 soldiers to a village of Cheyenne under cover of night. Chivington ambushed them knowing that their chief, Black Kettle, had been invited to camp with his people at Sand Creek by a local fort commander, and that only a handful of warriors would be present. There were a few soldiers who had honor: U.S. Captain Silas Soule and Lieutenant Joseph Cramer refused to participate in the act of genocide and ordered their men to stand down. In a letter to his mother, Soule wrote that some 300 Cheyenne were massacred that day, and that “most of them were women and children.” Soule’s account in a separate letter to an army major reveals just how grisly the attack was. “Hundreds of women and children were coming towards us, and getting on their knees for mercy,” he wrote, only to be shot and “have their brains beat out by men professing to be civilized.” Cheyenne men, women, and children were shot, chased down, and hacked to pieces. Unborn babies were ripped from their mothers’ wombs. Soldiers cut out women’s genitals as trophies, and paraded through the streets of Denver, Colorado, displaying human body parts carved from the mutilated dead. Soule was later assassinated, likely by associates of Chivington.

There was more darkness ahead for the Cheyenne people and Black Kettle. Four years later, on November 27, 1868, George Armstrong Custer attacked Black Kettle’s village along the banks of the Washita River, even though the villagers were flying a white flag of peace. The people were still sleeping when Custer commanded his men to charge. Dozens were shot and killed within minutes. More than 100 Cheyenne were slaughtered, including Black Kettle himself. Custer also ordered the killing of everything of value to the Indians, including 800 horses and mules. Historians say Custer committed the atrocity to help seal his reputation as an Indian fighter. His vile exploits eventually caught up with him at a place my ancestors call Greasy Grass, along the Little Big Horn River, where he and his men were rubbed out by Lakota and their allies.