CNN  — 

White House chief of staff John Kelly grew so frustrated on the day Veterans Affairs Secretary David Shulkin was fired that both Homeland Security Secretary Kirstjen Nielsen and Defense Secretary James Mattis attempted to calm him down, The Washington Post reported Saturday, in a story based on interviews with more than a dozen administration officials and confidants and advisers to the President.

CNN has previously reported on tensions between the President and his chief of staff, including the fact that Kelly has threatened to quit in the midst of clashes with Trump, according to people familiar with the incidents. But Kelly has told allies that he believes it is his duty to help implement the President’s agenda.

Trump has started to bypass Kelly, who has sought to control access to the President, in a variety of ways, CNN has reported, such as in conversations with foreign leaders, policy decisions, and in executing recent staffing changes, according to individuals with knowledge of the matter. Kelly, meanwhile, has sought to bring further order to the policymaking process, including by naming Chris Liddell as his deputy for policy implementation.

Last month, Kelly even attempted to dispel rumors that he was on the outs with the President, telling aides “I’m in,” while Trump told advisers that his chief of staff was “100% safe.”

The Post reports that when Trump announced via Twitter last month that Shulkin would be replaced by his personal physician, Ronny Jackson, Kelly became so exasperated that Nielsen, his former deputy at the White House and chief of staff when he ran the Department of Homeland Security, and Mattis sought to calm him down, according to three individuals with knowledge of what happened. It’s unclear why Kelly was so frustrated, but the Post reports that he said, “I’m out of here, guys.”

A senior administration official told the Post that Kelly’s remarks only signified that he was heading home early from work, but the newspaper reported that some people viewed the remarks “as a resignation threat.”

In addition, the Post reports Kelly angered first lady Melania Trump with the firing of John McEntee, a longtime aide to the President, in March. The Post, citing administration officials, reported Melania was “upset over his sudden dismissal” of the aide, who had come under investigation by the Department of Homeland Security for financial crimes. But the newspaper did not specify why McEntee’s departure caused her to become angry with Kelly.

Melania Trump’s name has been linked to West Wing staffing departures in the past, as it was when former chief of staff Reince Priebus was fired last summer; however, a White House source at the time strongly denied to CNN that the first lady was involved in any decisionmaking process.

“She has more important things to do,” the source said.

A spokesperson for Melania Trump did not immediately return CNN’s request for comment on the Post’s report Saturday night.

CNN’s Abby Phillip, Dan Merica, Jeff Zeleny, Jim Acosta, Kaitlan Collins, Kevin Liptak, Kate Bennett and Catherine Treyz contributed to this report.