President Donald Trump started off the week by mocking one of the worst Native American massacres in US history in order to score some political points. By Friday, a group of young white teenagers were following his footsteps by taunting Native American elders at the Indigenous Peoples March in Washington, DC — on the steps of the Lincoln Memorial, no less.

In videos shared widely on YouTube and Twitter, a young man wearing a self-assured smirk and a red “Make America Great Again” stands inches away from a native elder who is beating a drum. Different angles of the incident show a group of a few dozen young people, mostly boys, in the background, jumping up and down and jeering in unison at the group of elders present for the day’s march. In some shots, the teens appear to be shouting “build that wall, build that wall.”

The boys’ school announced late Saturday that it is now investigating the incident to see what punishment for the students is appropriate — even expulsion is on the table.

According to Vincent Schilling from Indian Country Today, the elder targeted in the video clip is Nathan Phillips, a Vietnam veteran and former director of the Native Youth Alliance. Phillips is a keeper of a sacred pipe, Schilling reports, and each year hosts a ceremony honoring Native American veterans at Arlington National Cemetery. The commemoration coincided Friday with the first annual Indigenous Peoples March, which was organized by a coalition of tribal councils, activists and youth leaders to raise awareness on issues facing their community, from police brutality to mental wellness to violence against women.

More video shows Phillips wiping away tears in reaction to the harassment.

“This is Indigenous land you know, we’re not supposed to have walls here. We never did for millenniums — before anybody else came here we never had walls,” he says in the clip. “I wish I could see that energy in that young mass of young men down there. To put that energy into making this country really, really great — helping those that are hungry.”

The teenagers in the clip have yet to be identified, though young men in the background appear to be wearing clothing with the insignia for Covington Catholic High School in Park Hills, Kentucky. The Diocese of Covington and Covington Catholic High School on Saturday afternoon condemned the harassment and said in a statement that an investigation is underway and “we will take appropriate action, up to and including expulsion.”

“We extend our deepest apologies to Mr. Phillips. This behavior is opposed to the Church’s teachings on the dignity and respect of the human person,” the statement said.

The episode casts a dark shadow over the March for Life, an annual anti-abortion demonstration that drew thousands of protesters and surprise appearances Friday from Trump and Vice President Mike Pence. The students had traveled to Washington, DC to attend the gathering, which held competing rallies on the day of the Indigenous Peoples March. It was after demonstrations had begun to die down that the students began harassing the Native American elders in the video.

“We know this incident also has tainted the entire witness of the March for Life and express our most sincere apologies to all those who attended the March and all those who support the pro-life movement,” the diocese and school statement continues.

The video was met with swift outrage and disgust online.

Rep. Deb Haaland, one of the first two Native American women elected to Congress, tweeted on Saturday calling the incident “heartbreaking” and a display of “blatant hate and disrespect.”