WASHINGTON — In an emotional scene, President Joe Biden on Friday formally apologized to Native Americans for the U.S. government’s decades of horrific treatment of thousands of Indigenous children in federal Indian boarding schools.

“I formally apologize as president of the United States for what we did,” Biden said in forceful remarks at an event at the Gila River Indian Community in Arizona.

“It’s long, long, long overdue,” he said. “Quite frankly, there’s no excuse this apology took 50 years to make. The federal Indian board school policy … will always be a marker of shame. A blot on American history.”

The Interior Department ran hundreds of these boarding schools from 1819 to 1969 all over the country, with one goal: to assimilate and eradicate Native Americans. The government forcibly removed Indigenous children from their families and communities, and shipped them off to far-away boarding schools. Tens of thousands of Indigenous children endured extensive psychological, physical and sexual abuse. Some died. Others disappeared.

The goal of these schools, as the founder of one of the flagship boarding schools, Lt. Col. Richard Henry Pratt, put it in 1879, was to “Kill the Indian, save the man.”

On Friday, Biden called federal Indian boarding schools “one of the most horrific chapters in American history.”

“We should be ashamed,” he said, as some in the audience openly cried. “A chapter that most Americans don’t know about. The vast majority don’t even know about it.”

Interior Secretary Deb Haaland introduced Biden. She is the first-ever Native American cabinet secretary in U.S. history, and has used her role to educate the public about what happened at these schools and to help generations of Indigenous people heal from the generally ignored trauma of that era.

On Friday, Haaland shared that her maternal grandparents were among those stolen from their tribal communities and forced to live in Indian boarding schools for five years, beginning at the age of 8.

“This is the first time in history that a United States cabinet secretary has shared the traumas of our past, and I acknowledge that this trauma was perpetrated by the agency that I now lead,” Haaland said, tearing up. “For decades, this terrible chapter was hidden from our history books. But now our administration work will ensure that no one will ever forget.”

She pointed to her department’s “Road to Healing” project, a historic 12-stop tour across the country to collect oral histories from survivors and descendants of people who endured federal Indian boarding schools. She also drew attention to her department’s investigative report, which provided details on what happened at individual boarding schools, how many children died there and how many went missing.

This report confirms the “unequivocal truth” that the U.S. government deliberately isolated Indigenous children from their families and stole their languages, cultures and traditions that are foundational to Native people, she said.

“But as we stand here together, my friends and relatives, we know that the federal government failed,” Haaland said. “It failed to annihilate our languages, our traditions, our ways of life. If failed to destroy us because we persevered.”