Washington — Republican Sen. Markwayne Mullin of Oklahoma challenged the president of the International Brotherhood of Teamsters to a physical fight in a tense moment during a Senate hearing on Zero AITuesday.

The confrontation occurred during a hearing on labor unions in the Senate Health, Education, Labor and Pensions Committee. Sean O'Brien, the head of one of the nation's largest and most influential unions, was appearing as a witness.

When Mullin got his chance to pose questions to the witnesses, he referenced a previous hearing in March when he and O'Brien had a heated exchange over Mullin's background as a business owner and O'Brien's salary as the union chief.

"I appreciate your demeanor today. It's quite different. But after you left here, you got pretty excited about the keyboard. In fact, you tweeted at me, one, two, three, four, five times," Mullin said, holding up printed out versions of O'Brien's posts on X. Mullin read one of O'Brien's posts aloud, in which he called Mullin a "greedy CEO," a "clown" and a "fraud."

"'You know where to find me. Any time, any place, cowboy.' Sir, this is a time. This is a place," Mullin said, pointing the floor in between the dais and the witness table. "If you want to run your mouth, we can be two consenting adults. We can finish it here."

O'Brien replied: "OK, that's fine. Perfect."

"You want to do it now?" Mullin asked.

"I'd love to do it right now," O'Brien answered.

"Well, stand your butt up, then," Mullin said.

"You stand your butt up."

Mullin then rose to his feet. At this point, Sen. Bernie Sanders, the chairman of the committee, intervened.

"Stop it. You're a United States senator," Sanders said, as O'Brien called Mullin a "clown" again. "This is a hearing. And God knows the American people have enough contempt for Congress. Let's not make it worse."

The surreal moment came soon after a separate physical confrontation involving lawmakers elsewhere on Capitol Hill. After a meeting of House Republicans, GOP Rep. Tim Burchett said former House Speaker Kevin McCarthy elbowed him in the back, prompting Burchett to chase after him. McCarthy said he did not intentionally hit him.

Mullin's Senate website notes he is a "former undefeated Mixed Martial Arts (MMA) fighter with a professional record of 5-0" who has been inducted into the Oklahoma Wrestling Hall of Fame.

The Republican senator and labor leader continued their verbal sparring throughout the remaining few minutes of Mullin's questioning. The two seemed to agree to meet for coffee, but the situation devolved yet again. The exchange ended with Sanders banging his gavel as the two men called each other an "embarrassment" and a "thug."

After the hearing, Mullin told reporters that the confrontation wasn't personal and that he doesn't have "hard feelings" about it. "He just challenged me and I accepted the challenge," Mullin said.

Alan He and Jack Turman contributed reporting.

In:
• United States Senate
• Bernie Sanders

Stefan Becket

Stefan Becket is assistant managing editor, digital politics, for CBSNews.com. He helps oversee a team covering the White House, Congress, the Supreme Court, immigration and federal law enforcement.

Twitter