KEY POINTS
  • Sen. Markwayne Mullin, R-Okla., told a union leader to "shut your mouth" during a Senate committee hearing on Wednesday.
  • Mullin, who owns a plumbing business, accused witnesses of failing to defend business owners against intimidation from union members.
Sean OBrien, the incoming leader of the International Brotherhood of Teamsters (IBT), at IBT headquarters in Washington, D.C,, U.S., on Thursday, March 17, 2022.

WASHINGTON — A Republican lawmaker Wednesday told Teamsters General President Sean O'Brien to "shut your mouth" in a terse exchange at a hearing examining so-called union busting by U.S. companies.

The tense back-and-forth between O'Brien and Sen. Markwayne Mullin, R-Okla., escalated into a screaming match at a hearing before the Senate Health, Education, Labor and Pensions Committee.