As Donald Trump’s West Wing careens through one of the most turbulent weeks of his presidency, White House officials are struggling to understand the source of the fury fueling the president’s eruptions. “This is a level of insanity I’ve never seen before,” one former West Wing staffer told me. Current and former officials are debating different theories for Trump’s outbursts, ranging from his fears over his son Don Jr.’s legal exposure to the prospect that House Democrats will unleash investigations in January. “He’s under a tremendous amount of mental stress,” one prominent Republican close to him told me.

What’s surprising to some advisers about how bad the past week has been is that Trump initially seemed to take the midterm losses in stride. Last Tuesday, he was in high spirits as he watched election returns come in with about a hundred friends at the White House. Trump told people that his barnstorming rally schedule had mobilized his base and held Republican losses to historical lows, while increasing Republican gains in the Senate. “He really thought he won the midterms,” a prominent Republican who spoke with Trump said.

But by Wednesday, after hours of commentary about the suburbs’ distaste for him and with seat after undecided House seat slipping toward the Democrats, his mood slid, too, hitting bottom in a bizarre and combative press conference. “He was furious about the narrative. He said, ‘Look, I went to all these states and now people are saying Trump lost the election,’” the Republican who spoke with him recalled. Within hours, Trump forced out Attorney General Jeff Sessions and replaced him with Matt Whitaker, who’d been a frequent cable-news critic of the Robert Mueller investigation. Next, Trump directed his press office to revoke CNN reporter Jim Acosta’s press pass, something he’d wanted to do for months but had been talked out of by aides. “This is a matter of the president now being on his own without any countervailing force whatsoever,” a person close to Trump said. “It’s just 100 percent Donald Trump doing what Donald Trump wants.”

Trump remained in a dark mood during his weekend trip to France to mark the 100th anniversary of the end of World War I. As The Washington Post reported, he got into an argument with British Prime Minister Theresa May during a phone call on the flight across the Atlantic on Friday. On Saturday morning, Trump skipped attending a rain-soaked ceremony at the Aisne-Marne American Cemetery to honor the Battle of Belleau Wood. When his absence became a scandal, the White House said the decision had been made because Marine One reportedly could not fly in the rain, and Secret Service did not want Trump traveling by motorcade. One Republican briefed on the internal discussions said the real reason Trump did not want to go was because there would be no tent to stand under. “He was worried his hair was going to get messed up in the rain,” the source said. “[John] Bolton and everyone was telling him this was a big mistake.” A former administration official said Trump hates being outside in wet conditions. “What I honestly think? He woke up and said, ‘It’s pouring rain. This is a joke and I’m not doing this.’”

Trump’s absence from the ceremony became the dominant headline from his trip. Perhaps as a gambit to change the subject, Trump fumed on the flight back to Washington that he was ready to fire embattled Homeland Security Secretary Kirstjen Nielsen, whom he has clashed with over the uptick in border crossings. A move against Nielsen would be, in many ways, a chance for Trump to finally force Chief of Staff John Kelly, her closest administration ally, to quit. According to a source, Kelly told White House counselor Johnny DeStefano that he would resign if Trump fired Nielsen.