US Special Envoy to Northern Ireland Mick Mulvaney has resigned following violence at the US Capitol last night.
Donald Trump's former Chief of Staff told CNBC he couldn't stay in his position.
Mr Mulvaney said that others, who are choosing not to resign, are doing so as they worried President Trump may fill their position with "someone worse."
Mr Trump announced Mr Mulvaney's appointment as special envoy last March.
At the time he was the acting White House Chief of Staff.
Mr Mulvaney, who has roots in Co Mayo, was sworn in as Northern Ireland Envoy in May.