By ZEKE MILLER, AAMER MADHANI and SEUNG MIN KIM Associated Press

WASHINGTON (AP) — White House national security adviser Mike Waltz is leaving the administration just weeks after it was revealed he added a journalist to a Signal chat being used to discuss military plans, according to two people familiar with the matter Thursday, marking the first major staff shake-up of President Donald Trump’s second term.

Waltz came under searing scrutiny in March after revelations that he added journalist Jeffrey Goldberg to a private text chain on the encrypted messaging app Signal, which was used to discuss planning for a sensitive March 15 military operation against Houthi militants in Yemen. A far-right ally of the president, Laura Loomer, has also targeted Waltz, telling Trump in a recent Oval Office conversation that he needs to purge aides who she believes are insufficiently loyal to the “Make America Great Again” agenda.

Waltz’s deputy, Alex Wong, is also expected to depart, according to the people, who spoke on the condition of anonymity to discuss a personnel move not yet made public. The National Security Council did not respond do a request for comment.

Waltz, who served in the House representing Florida for three terms before his elevation to the White House, is the most prominent senior administration official to depart since Trump returned to the White House. In his second term, the Republican president had been looking to avoid the tumult of his first four years in office, during which he cycled through four national security advisers, four White House chiefs of staff and two secretaries of state.

The Signal chain also showed that Defense Secretary Pete Hegseth provided the exact timings of warplane launches and when bombs would drop. Waltz had previously taken “full responsibility” for building the message chain and administration officials described the episode as a “mistake” but one that caused Americans no harm. Waltz maintained that he was not sure how Goldberg ended up in the messaging chain, and insisted he did not know the journalist.

Trump and the White House — which insisted that no classified information was shared on the text chain — have stood by Waltz publicly throughout the episode. But the embattled national security adviser was also under siege from personalities such as Loomer, who had been complaining to administration officials that she had been excluded from the vetting process for National Security Council aides. In her view, Waltz relied too much on “neocons” — referring to hawkish neoconservatives within the Republican Party — as well as others who Loomer argued were “not-MAGA-enough” types.

Waltz was on television as late as Thursday morning, promoting the administration’s agreement with Kyiv that would allow the U.S. to access Ukraine’s critical minerals and other natural resources. As reports began to circulate that Waltz could be leaving the administration, Loomer appeared to take credit in a post on the social media site X, writing: “SCALP.”

“Hopefully, the rest of the people who were set to be fired but were given promotions at the NSC under Waltz also depart,” Loomer wrote in another post.

Loomer had taken a similar victory lap when several other NSC officials were dismissed last month one day after she met with Trump. Those firings included Brian Walsh, a director for intelligence; Thomas Boodry, a senior director for legislative affairs; and David Feith, a senior director for technology and national security, as well as other lower-ranking aides.

Waltz’s resignation comes as questions are swirling around Hegseth and his role in the Signal chat.

While Waltz set it up, Hegseth posted times for aircraft launches and bomb drops into the unsecured app and shared the same information with dozens of people in a second chat, including his wife and brother.

The Associated Press reported that Hegseth also bypassed Pentagon security protocols to set up an unsecured line for a personal computer in his office –- beside terminals where he was receiving classified information. That raises the possibility that sensitive information could have been put at risk of potential hacking or surveillance.

The Pentagon inspector general is investigating Hegseth’s use of Signal, and he has faced criticism from Democrats and even some Republicans. It has added to the turmoil at the Pentagon at a time when Hegseth has dismissed or transferred multiple close advisers. Nonetheless, Trump has maintained public confidence in Hegseth.

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Associated Press writer Tara Copp contributed to this report.