Washington (CNN) By the start of John Bolton's second week as national security adviser, five top officials at the National Security Council had already resigned under pressure, been fired or decided to leave.

But even as the White House cites Bolton's desire -- and right -- to build his own team, he has yet to announce a single senior hire to replace the departing officials. Instead, he has kept his new staff guessing -- feeding a sense of uncertainty and anxiety that has filled NSC offices since his arrival.

Following a series of departures, senior and midlevel officials were left wondering who would be next after they were told their résumés were under review by the new boss.

The latest departure came Monday with the White House's acting deputy homeland security adviser Rob Joyce giving notice of his departure, Marc Raimondi, an NSC spokesman, told CNN.

"Nobody told him that he has to leave," Raimondi said. "He just realizes that it's time for him to go back to NSA. It's not imminent and it's not forced."

White House press secretary Sarah Sanders said Joyce "conveyed his intent to return to his home agency" and would help with the transition. Joyce called his work as the White House's cybersecurity coordinator "a tremendous opportunity" and said in a statement he looks forward "to continuing to serving our nation at the agency I've called home for the last 27 years."

Just last week, Joyce's boss, White House homeland security adviser Tom Bossert, was pushed out.

And just like Bossert's, Joyce's exit was unexpected. The former head of the NSA hacking team Tailored Access Operations Unit was recently considered a possible choice to lead the National Security Agency as its first civilian director, one source said. And he gave notice of his plans to leave the NSC shortly before jumping on an official briefing call with reporters to discuss US monitoring of Russian hacking.

Sense of anxiety

There was a sense earlier Monday morning that morale was picking back up after a series of resignations and firings shook the NSC last week -- but the Joyce news reignited the anxiety, multiple sources close to the NSC told CNN. And that uncertain state of play comes as the administration is dealing with a host of urgent foreign policy issues, from the fallout of the US response to Syria's suspected chemical weapons attack to the prospect of direct talks with North Korea.

"No one knows what's going on," one source close to the NSC told CNN. "It's a bit chaotic."

The White House declined to comment on the chaotic nature of Bolton's transition and the anxiety his tenure has provoked among some in the NSC.

Two days after the NSC's chief spokesman, Michael Anton, resigned after learning Bolton planned to fire him, Bossert was ousted hours after leaving a national security conference on the administration's behalf. The next day, the deputy national security adviser for strategy, Nadia Schadlow, told her staff she had resigned. The following day, it was deputy national security adviser Ricky Waddell's turn to submit a letter of resignation.

The latter two won't leave their posts immediately, to ensure a smooth transition, but despite the slew of departures Bolton has yet to announce a single new hire, and his advisers outside the White House have kept quiet about who will fill out senior roles at the NSC.

"It makes sense for Bolton to think about bringing in his own NSC staff leaders, like the people in senior director roles, which are often political. That's typical," Loren Schulman, the director for defense policy at the NSC from 2011 to 2012, told CNN. "But a 'purge' as people are talking about of the director level staff -- usually detailees from other agencies -- makes no sense."

While the NSC's human resources staff has begun to compile résumés for Bolton's review, the national security adviser spent much of his first week in meetings with President Donald Trump or his coterie of top foreign policy advisers deliberating the US response to the use of chemical weapons in Syria.

But even before his official start, an orderly transition didn't appear to be top of mind for Bolton, who didn't meet with the NSC official who former national security adviser H.R. McMaster had designated to help with the transition until last Thursday -- the day before McMaster left the White House for good. Bolton additionally did not meet with the rest of the professional staff prior to starting.

High turnover

JUST WATCHED Bolton faces Syria challenge in new NSC role Replay More Videos ... MUST WATCH Bolton faces Syria challenge in new NSC role 04:41

While it's normal for Bolton to hire some of his own trusted advisers, the high turnover at the National Security Council is unusual. During President Barack Obama's tenure, about 90% of the employees at the NSC were career professionals on rotation, collating advice for the President from their different agencies and experts for one or two years before returning.

When McMaster took over from Lt. Gen Michael Flynn as Trump's second national security adviser, he took his time but also fired some controversial NSC officials including Rich Higgins, the alleged author of a memo about the "deep state." Other NSC members resigned.

"We did our best to try to have a responsible transition and handoff. But his team just really didn't seem interested in that," a former NSC official said. "Does he have a team that he can replace the current people with? And will they be ready to be in place by the time the current team is gone?" While those officials are certain to have home agencies to return to, they are uncertain what their day-to-day lives will be like under Bolton.

A second former NSC official expressed concern that the politicization had gone too far -- and that people McMaster fired might resurface in new roles now he's gone.

The uncertainty has sent morale plummeting to "Flynn level lows," one source close to the NSC said, referencing the chaotic firing of Trump's first national security adviser.

"It's a counter purge to the McMaster purge ... it's just a sad state of affairs," a second source close to the NSC said.

The pace of firings and resignations, compounded by a lack of new hires, has also flummoxed and frustrated the West Wing. One senior White House official lamented the staff shake-up's haphazard nature, though White House Director of Social Media Dan Scavino Jr. gleefully tweeted his support of Bolton's purge: "Look out leakers, here comes Bolton!"

Instead of firm signals from Bolton, rumors of a "list" of officials he intends to fire have abounded.

Brian McKeon, the NSC's chief of staff from 2012 to 2014, conceded that Bolton has the discretion to fill appointments but worried the the tumultuous transition would be disruptive.

"I don't think it makes sense to have so much tumult immediately," McKeon said. "To have all these deputies leaving nearly simultaneously is a big disruption, given the amount of work that goes on at the deputy level."

Staying in the loop

JUST WATCHED Trump jokes about another firing Replay More Videos ... MUST WATCH Trump jokes about another firing 00:38

The state of play has also contributed to confusion about at least one major decision, with the top staffers handling Latin America issues finding out that Trump was canceling his trip there via White House press release, two sources said. In this administration, it isn't uncommon for the NSC to be left out of the loop, but the timing compounded the current sense of frustration.

The NSC can't force the policy makers it serves to keep it in the loop, Schulman told CNN.

"We've seen before that in moments of distraction or leadership vacuums the Trump administration is pretty bad at announcing and implementing complex decisions," Schulman said.

NSC officials have also complained about struggling to coordinate policymaking with the national security adviser's front office, which saw several key aides depart at the same time as McMaster.

Ylli Bajraktari, the former special assistant to Pentagon Deputy Secretary Bob Work hired to the NSC by McMaster, Megan Badasch, the NSC's deputy executive secretary, and Fernando Cutz, the former director for South America who moved to McMaster's front office last summer, all departed on McMaster's last day.

"There is a lot of anxiety in the NSC about Bolton and a wait and see attitude about whether he actually understands the role of the national security adviser -- to honestly collect and represent diverse agency views and present them to POTUS," one of the sources said. "Folks aren't hopeful so far."

Now, officials are bracing themselves for more departures.

Schadlow's staff has "no idea what's going on" and is unsure of their future at the NSC, the source said. And "almost every senior director is pretty nervous," another source said. One current NSC official worried a "purge" was coming to bear.

"A big mistake the administration has made is to see career foreign service officers and civil servants as the enemy, part of some fictitious deep state opposed to Mr. Trump," Tony Blinken, former national security adviser to Obama, told CNN.

"To the contrary, they are patriots who want the success of whichever administration they are working for."