(CNN) A crowd of teenagers surrounded a Native American elder and other activists and appeared to mock them after Friday's Indigenous Peoples March at the Lincoln Memorial.

Videos of the confrontation show a smiling young man in a red Make America Great Again hat standing directly in front of the man, who was playing a drum and chanting. Other kids could be seen laughing, jumping around and seemingly making fun of the chants.

Nathan Phillips, an elder with the Omaha tribe, said the confrontation felt like "hate unbridled." In the moment, he said he was scared for his safety and the safety of those with him.

The behavior of the students from Covington Catholic High School -- an all-boys' school in Northern Kentucky -- triggered widespread condemnation from lawmakers and celebrities as well as the school district, the mayor of the neighboring town and Covington's Roman Catholic Diocese.

"I was not intentionally making faces at the protester. I did smile at one point because I wanted him to know that I was not going to become angry, intimidated or be provoked into a larger confrontation. I am a faithful Christian and practicing Catholic, and I always try to live up to the ideals my faith teaches me -- to remain respectful of others, and to take no action that would lead to conflict or violence."

He cautioned against rushing to judgment based on the short time captured on the videos and encouraged people to watch longer clips available online, "as they show a much different story than is being portrayed by people with agendas," he said.

"I am mortified that so many people have come to believe something that did not happen -- that students from my school were chanting or acting in a racist fashion toward African-Americans or Native Americans. I did not do that, do not have hateful feelings in my heart, and did not witness any of my classmates doing that."

The person who shot the videos described the atmosphere as tense.

Kaya Taitano, a student at the University of the District of Columbia, participated in the Indigenous Peoples March earlier in the day. She said the teens were chanting things like "Build the wall" and "Trump 2020." Those chants were not audible in videos reviewed by CNN.

"I did not feel safe in that circle," she said.

Taitano said the whole incident started when the teens and four young African-Americans, who'd been preaching about the Bible nearby, started yelling and calling each other names.

Another video shot before the encounter shows men who identify as members of the Hebrew Israelites taunting the students and other passersby with racist slurs.

It got pretty intense, Taitano said, so Phillips started playing his drum and chanting what she was told was a healing prayer, to help defuse the situation.

Phillips walked through the crowd, and Taitano said things were starting to calm down until he got to the grinning boy seen in the video.

"This one kid just refused to move and he just got in Nathan's face," she said.

Other boys circled around, she said. "They just surrounded him and they were mocking him and mocking the chant. We really didn't know what was going to happen there."

Phillips served in the US Marine Corps Reserve from 1972 to 1976, according to his service record obtained by CNN. He told CNN that he was a "Vietnam-era" veteran. The USMC says he was never deployed during his service.

"I was scared, I was worried for my young friends. I don't want to cause harm to anyone," Phillips told CNN's Sara Sidner. "I don't like the word 'hate.' I don't like even saying it, but it was hate unbridled. It was like a storm."

The crowd kept growing as Phillips and the boy stood face to face, but Phillips kept on chanting and playing his drum.

"What the young man was doing was blocking my escape. I wanted to leave. I was thinking, 'How do I get myself out of this? I want to get away from it,'" Phillips said.

But Sandmann said it was clear to him that Phillips had singled him out for a confrontation, although he was not sure why.

He said the incident began when a group identifying themselves as the Hebrew Israelites began to shout disparaging and vulgar comments at his group. He said the students began using school spirit chants -- with permission from teachers -- in response to the taunts.

He denied that anyone in the group said "build the wall" or used hateful or racist language toward Phillips.

"Our chants were loud because we wanted to drown out the hateful comments that were being shouted at us by the protesters," he said.

"The protester everyone has seen in the video began playing his drum as he waded into the crowd, which parted for him. I did not see anyone try to block his path. He locked eyes with me and approached me, coming within inches of my face. He played his drum the entire time he was in my face," Sandmann said.

"I never interacted with this protester. I did not speak to him. I did not make any hand gestures or other aggressive moves. To be honest, I was startled and confused as to why he had approached me. We had already been yelled at by another group of protesters, and when the second group approached I was worried that a situation was getting out of control where adults were attempting to provoke teenagers."

Taitano said the standoff continued until a chaperone came and led the teens away for a photograph.

The school's website said a group of students had planned to attend Friday's March for Life rally in Washington.

The school is part of the Roman Catholic Diocese of Covington, and in a statement given to CNN affiliate WLWT , spokeswoman Laura Keener said the diocese would investigate the incident and take appropriate action.

"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. This behavior is opposed to the Church's teachings on the dignity and respect of the human person.

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

CNN has reached out to the school and diocese for comment.

Taitano, who is from Guam, said she was raised to treat her elders with respect so it hurt to see them treat Phillips so badly.

Phillips also appeared upset in a video Taitano posted after the confrontation. He wiped away tears as he talked about the students' actions.

"I wish I could see that energy of the young mass of young men to, you know, put that energy into, you know, making this country really, really great by helping those who are hungry, you know," Phillips said.

Correction: This article has been updated to remove wording that Phillips is a Vietnam veteran. He did serve in the military during the Vietnam War, but according to his service records, he was not deployed to Vietnam.