DENVER (CBS4) – A fight broke out in the middle of the Bernie Sanders rally on Sunday evening at the Colorado Convention Center. The Democratic presidential candidate rallied thousands of supporters in Denver in a campaign stop before the March 3 Colorado primary.

CBS4’s news camera was capturing video of the event when two men began fighting. They pushed through a metal barrier fence toward the back near the media risers as they grappled with each other and one man knocked the other down onto the ground after lifting him up.

Friends of both people quickly intervened and after some more shoving successfully broke up the fight.

It wasn’t immediately clear to CBS4’s crew what the two men were fighting about, but someone contacted CBS4 on Monday by phone and said he is a Sanders supporter and one of the people involved. He said his name is Tyler and that a person with a T-shirt on that read “Black Guns Matter” was with two other men and they were booing during the speech. When Tyler tried to capture video of the booing on his phone’s camera, the man shoved him through the barrier. Tyler then retaliated. It was that action which was captured by CBS4’s camera.

Another video provided to CBS4 by an anonymous viewer shows the moments leading up to the brawl. It allegedly shows Tyler, in a jeans jackets, and another man arguing about the man’s shirt. That man with the “Black Guns Matter” shirt also contacted CBS4, although anonymously. He called Tyler the aggressor. The other man identified himself as African American.

“He had a problem with the shirt I was wearing,” this man said. “I was recording the event, he walks up and calls me a racist. But I thought, ‘What’s he know about black lives, about discrimination, or, for that matter, the representation of the shirt.'”

Throughout American history, the man continued, “Black people and their ability to own firearms has historically been very restricted. The shirt I got from a conceal-carry class.”

He said he agrees with Sanders on a number of policies but definitely not on gun ownership.

“I think it’s really a sad thing at a Bernie rally, when someone has a difference of opinion, that someone would be treated like that. I thought it really would be a lot more inclusive than that. It’s not a safe place to express differences. I would expect that sort of thing at a Trump rally.”

Neither one of the men was escorted out — security instead chose to instruct them to separate from each other in the crowd.

Sanders didn’t pause during his speech at any point during the fight.

PHOTO GALLERY: Bernie Sanders Campaign Rally In Denver