Disturbing videos emerged Saturday that appear to show Kentucky high school students mocking participants of the Indigenous Peoples March in Washington, D.C.—including a widely respected Native American elder who served in Vietnam.

The videos went viral on social media and drew widespread condemnation—and, eventually, an apology from the all-boys’ school that sent the teens to the nation’s capital for the March for Life on Friday.

“This behavior is opposed to the Church’s teachings on the dignity and respect of the human person,” Covington Catholic High School and the Diocese of Covington said in a joint statement.

“The matter is being investigated and we will take appropriate action, up to and including expulsion.”

The videos that sparked outrage show Covington Catholic High School students, some of them wearing “Make America Great Again” gear, surrounding a group of Native American marchers and shouting and jumping as marchers start playing music.

One boy in a MAGA hat appears to stand just inches from the face of Omaha tribe elder Nathan Phillips, who is singing and playing a drum. Phillips smiles calmly at the teen and continues to play.

“When I was there singing, I heard them saying, ‘Build that wall! Build that wall!’” Phillips said later in a video posted to Twitter. “This is indigenous land—not supposed to have walls here. We never [did] for millennium.”

“Before anybody else came here, you never had walls, you never had a prison,” he also said. “We always too care of our elders. We took care of our children.”

Phillips, the previous director of the Native Youth Alliance, is a “keeper of a sacred pipe” who leads an annual ceremony honoring Native American veterans in Arlington National Cemetery, according to Indian Country Today.

Phillips said he wished the young men’s energy was used “to making this country really great.”

Defenders of the teens on social media circulated a snippet that showed Phillips approaching the school group at one point—along with screenshots of text messages purported to be from the boys in which they claimed he was the interloper and they were only being enthusiastic.

Phillips later said he'd approached the group of students after seeing a confrontation brewing between them and a separate group of religious protesters believed to be affiliated with the Black Hebrew Israelite movement. Videos posted to YouTube showed members of that group taunting the students before Phillips walked up and began drumming.

“Something caused me to put myself between (them) — it was black and white,” Phillips was quoted as saying by the Associated Press on Sunday. “What I saw was my country being torn apart. I couldn’t stand by and let that happen.”

Marcus Frejo, a member of the Pawnee and Seminole tribes, told the Associated Press that he and Philips saw the students chanting “Make America great” and doing a mocking version of the haka, the traditional Maori dance, and decided to go over to defuse the situation.

However the two groups crossed paths, the clip of the student wearing the MAGA hat and a smirk on his face, standing in front of and staring at Phillips, drew widespread criticism.

New Mexico Democrat Deb Haaland, one of the first Native American women to serve in Congress, slammed the Covington students on Twitter.

“This veteran put his life on the line for our country,” she said. “The students’ display of blatant hate, disrespect, and intolerance is a signal of how common decency has decayed under this administration. Heartbreaking.”

Kentucky Secretary of State Alison Lundergan Grimes condemned the students’ behavior in a Facebook post, but largely placed the blame on the adults who shape their lives.

“In spite of these horrific scenes, I refuse to shame these children. Instead I turn to the adults that are teaching them and those that are silently letting others promote this behavior. This is not the Kentucky I know and love. We can do better and it starts with better leadership,” Grimes wrote.

As the videos began to circulate, the diocese said it was investigating. But as the criticism mounted, with public officials and celebrities joining in, the church and school issued the apology.

“We condemn the actions of the Covington Catholic High School students towards Nathan Phillips specifically, and Native Americans in general, Jan. 18, after the March for Life, in Washington, D.C. We extend our deepest apologies to Mr. Phillips,” it said.

The March for Life, an anti-abortion rally, was held at the same time as the Indigenous Peoples March. In a statement posted to Twitter, March for Life President Jeanne Mancini distanced itself from the Covington contingent.

“The pro-life movement at its core is a movement of love and the reprehensible behavior shown in the video in no way represents the 46 years and millions of people who have peacefully and respectfully gathered in Washington, DC, to stand up for the unborn,” she wrote.

Covington Catholic also apologized to March for Life participants, saying, “We know this incident also has tainted the entire witness of the March for Life and express or most sincere apologies to all those attended the March and all those who support the pro-life movement.”

On the Catholic Conference of Kentucky website, many Catholics called for the boys to be expelled.

“As a practicing Catholic and parent I can only pray that these children are expelled and the adult chaperones face severe consequences. This behavior brought me to tears,” a commenter named Julia Delgado wrote.

Editor’s note: An earlier version of this story incorrectly described Phillips as a Vietnam veteran. Phillips told The Washington Post he served in the U.S. Marines but never deployed to Vietnam.