Sanders intervenes after Republican senator challenges union boss to fight

Senator bangs gavel and calms tensions after Markwayne Mullin asked Teamsters' Sean O'Brien if he wanted to 'finish it here'

An Oklahoma senator and a union boss squared off in a congressional hearing on Tuesday, each daring the other to stand your butt up" and fight in an exchange the chair of the Senate labor committee, Bernie Sanders, struggled to contain.

Sit down!" Sanders shouted at Markwayne Mullin, the Republican on the dais beside him. You're a United States senator!"