Top Trump security adviser Tom Bossert resigning

President TrumpDonald John TrumpComey: Trump's 'Spygate' claims are made up Trump taps vocal anti-illegal immigration advocate for State Dept's top refugee job Seattle Seahawks player: Trump is 'an idiot' for saying protesting NFL players 'shouldn’t be in the country' MORE’s top homeland security aide, Tom Bossert, is resigning, the latest in a long line of staffers to exit the West Wing.

"The president is grateful for Tom's commitment to the safety and security of our great country,” White House press secretary Sarah Huckabee Sanders said in a statement.

“President Trump thanks him for his patriotic service and wishes him well,” she added.

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Bossert has served in the White House since Trump’s inauguration and played a key role in responding to cyber threats and last year’s hurricanes that devastated Texas, Puerto Rico and the U.S. Virgin Islands.

Homeland Security Secretary Kirstjen NielsenKirstjen Michele NielsenImmigrant women, children abused by gangs need our protection ‘Whatever’ isn’t an option for immigrant children Hillicon Valley: Trump claims 'no deal' to help Chinese company ZTE | Congress briefed on election cyber threats | Mueller mystery - Where's indictment for DNC hack? | Zuckerberg faces tough questions in Europe MORE praised Bossert for providing “wise counsel” to Trump on a “range of current and emerging threats to our nation.”

His departure comes one day after John Bolton took over as national security adviser, a move that was expected to cause turnover on Trump’s security team. The 43-year-old aide is close to chief of staff John KellyJohn Francis KellyMORE and Bolton’s predecessor, H.R. McMaster.

National Security Council spokesman Michael Anton announced his resignation two days before Bossert quit.

A veteran of the George W. Bush administration, Bossert was one of the few Trump aides to have previous White House experience.

Trump turned to Bossert in times of crisis, dispatching him to the White House briefing room and Sunday political talk shows to detail the administration’s relief efforts during last summer’s storms.

He also took the lectern at the White House to announce the U.S. had blamed North Korea for the massive “WannaCry” cyberattack that affected hundreds of thousands of computer across the world.

The timing of Bossert’s exit appeared abrupt.

He appeared on ABC News’s “This Week” on Sunday to speak about the administration’s response to the chemical weapons attack in Syria.

Bossert was also a keynote speaker Sunday night at The Cipher Brief's conference of national security experts in Sea Island, Ga. His remarks strongly suggested he did not expect to be forced out. 

“The only thing that creates instability or the perception of it is (a) the [media] coverage, and (b) the turnover, and I think at this point we’ve reached what seems to be a decent stability point," Bossert said when asked what it is like to work in the White House. "I’m pretty comfortable with the president’s view of that, but it’s a little different.”

His departure continues the wave of staff turnover that has rocked the Trump administration.

Just last month, McMaster, Secretary of State Rex TillersonRex Wayne TillersonFive takeaways on the canceled Trump summit with Kim Dem lawmaker confronts Pompeo over spending cuts to diplomatic security GOP fundraiser subpoenas AP over source of leaked emails: report MORE, economic adviser Gary CohnGary Davivd CohnTrump urged postmaster general to double rates on Amazon: report Overnight Finance: Deal on Dodd-Frank rollback | Trump pulls US out of Iran nuke deal | House votes to repeal auto-loan guidance, setting new precedent Gary Cohn: I feel 'freer' and 'happier' since leaving White House MORE, FBI Deputy Director Andrew McCabeAndrew George McCabeHouse GOP sets three FBI interviews in Clinton probe Trump: ‘Great’ people at FBI ‘starting to speak out against Comey, McCabe’ WATCH: NY Republican wants McCabe prosecuted MORE and Veterans Affairs Secretary David ShulkinDavid Jonathon ShulkinTrump admin gets lowest-ever ethics ratings in Gallup poll Senate panel heading toward June hearing for Trump's next VA pick Overnight Health Care — Sponsored by PCMA — Trump hits federally funded clinics with new abortion restrictions MORE were fired or tendered their resignations.

Top-level staff turnover at the White House has reached 49 percent, according to data compiled by Brookings Institution scholar Kathryn Dunn Tenpas, a number that has not been reached at this point in a presidency in decades.

Updated at 1:12 p.m.