A video of a brawl breaking out between two self-described Bernie fans, one white and one black, has gone viral — and initially inspired a bunch of assumptions about what started it, including that a “Trump supporter” infiltrated the event to stir up trouble. But a video posted later and a pair of interviews with two men claiming to be the ones involved indicate that the blow up was ultimately about the African-American man’s “Black Guns Matter” T-shirt, which the white “Bernie bro” condemned as “racist.”

The fight broke out during a Sanders rally held at the Colorado Convention Center in Denver Sunday evening. The initial fight was caught on camera by Colorado’s CBS4. The video of the sudden eruption of violence, which occurred at the back of the rally near the media risers, rapidly circulated online.

At last night’s Bernie Sanders rally in Colorado, the Bernie rally briefly turned into a Bernie vs Bernie brawl 😂😂 Notice in the background, Bernie’s speech is uninterrupted! 😂😂 pic.twitter.com/c6Dq8H24GZ — Shawnasaurus Rex (@ShawnG927) February 18, 2020

“CBS4’s news camera was capturing video of the event when two men began fighting,” CBS4 reported. “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. They both landed on the ground partially under the stage Sanders was in the middle of delivering his speech from. Friends of both people quickly intervened and after some more shoving successfully broke up the fight.”

CBS4’s crew said that they were initially unsure what started the scuffle, but on Monday, the outlet was contacted first by a man, Tyler, a self-described Sanders supporter who said he was the white guy shown duking it out in the video, then by another man who asked to remain anonymous who said he was the African-American man battling with Tyler. Another video involving the incident, this one before the fight broke out, shows Tyler and the African-American man arguing over the latter’s “Black Guns Matter” shirt.

The first to contact CBS4 Monday was “Tyler,” who told the outlet that a man with a “‘Black Guns Matter” shirt was with two other men “and they were booing during the speech,” CBS reports. “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.”

After the interview with Tyler, CBS4 was provided with a new video from an anonymous source showing the argument leading up to the blow-up. The outlet was then contacted by a man claiming to the “Black Guns Matter” shirt-wearer, who described himself as African-American and said the whole thing started over his shirt.

“He had a problem with the shirt I was wearing,” the man told CBS4. “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.'”

“Black people and their ability to own firearms has historically been very restricted,” he added. “The shirt I got from a conceal-carry class.”

The man also told CBS4 that he agrees with Sanders on most policies but not on guns.

“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,” he added. “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.”

Below is the video that appears to have been sent to CBS4: