The Department of Homeland Security’s acting deputy secretary resigned on Tuesday, following her boss in a White House-directed purge of U.S. immigration agencies.

The departure of Claire Grady, who has been undersecretary for management, clears the way for Kevin McAleenan, the current head of U.S. Customs and Border Protection, to take over as acting secretary of Homeland Security.

Her resignation was announced Tuesday night on Twitter by outgoing Homeland Security Secretary Kirstjen Nielsen, who herself was forced to resign on Sunday.

“Acting Deputy Secretary Claire Grady has offered the President her resignation, effective tomorrow,” Nielsen wrote. “For the last two years, Claire has served @DHSgov w excellence and distinction. She has been an invaluable asset to DHS – a steady force and a knowledgeable voice.”

President Donald Trump said McAleenan would take over the department on Sunday night, in a tweet announcing Nielsen’s departure after a series of disagreements with the White House over immigration enforcement.

Yet the decision to promote McAleenan came despite existing federal statute that seemed to dictate Grady was next in line for the job, leaving the appointment on shaky legal footing.

Earlier on Tuesday, the president downplayed his personnel moves at the Department of Homeland Security, saying he is fighting “bad laws” on immigration and obstruction in Congress.

“We have to close up the borders,” he told reporters after he was asked about the resignation of DHS Secretary during a meeting on Tuesday with Egyptian President Abdel-Fattah El-Sisi at the White House. “We’re not doing anything very big.”

Trump said he did not plan to reinstate a policy that led to the separation of thousands of migrant children from their families after they illegally crossed the border last summer. “We’re not looking to do that,” he said.

Nielsen resigned Sunday after meeting with Trump at the White House residence to discuss a spike in illegal crossings at the U.S. southern border. Trump is increasingly frustrated by the border crisis, and last month empowered a hard-line aide, Stephen Miller, to have greater authority over immigration policy within the White House.

A senior administration official told reporters in a briefing on Tuesday that the Homeland Security department is plagued by a dysfunctional bureaucracy, the result of Trump not having enough political appointees in key positions at the agency. The White House wants a crackdown on migrants seeking asylum at the southern border, the official said, because many of the claims are considered spurious.

More than 66,000 people were apprehended after crossing the border illegally in February, about a 38 percent increase from the month before. Most were families or children traveling alone.

The official said that Homeland Security could discourage migration by refusing to issue work permits to people in the country waiting for their asylum claims to be adjudicated. The claims themselves could be more rigorously vetted, the official said, to determine whether migrants’ assertions that they fear persecution in their home countries are credible.

‘Binary Choice’

The official also confirmed that the administration is considering a policy known as “binary choice.” It resembles family separation. Migrants would be asked to choose whether to be detained together with their children in facilities run by Immigration and Customs Enforcement or to be separated from their kids, who would be placed in the care of relatives, guardians or government-contracted shelters.

The policy isn’t fully developed yet, the official said.

Commander Jonathan White of the Public Health Service Commissioned Corps warned Congress on Tuesday that resuming family separations would harm children.

White told the Senate Homeland Security Committee that the corps has improved the tracking of people in its care. Still, he said, “We do not have the capacity to receive that number of children, nor do we have the capacity to serve them, nor is it possible to build a system that would prevent the mass traumatization of children.”

Senator Ron Johnson, a Wisconsin Republican and the chairman of the Homeland Security panel, said that “I would be completely opposed” to resuming the zero-tolerance border policy that resulted in the family separations. The policy caused outrage among lawmakers and the broader public before Trump halted the separations in June.

Kelly’s People

Miller is eyeing other people in the government who were hired after recommendations or referrals by Nielsen or former White House Chief of Staff John Kelly, two people familiar with the matter said.

Kelly preceded Nielsen at DHS and recommended her as his replacement. He departed the White House late last year after repeated clashes with the president.

Two other top officials at DHS — L. Francis Cissna, the head of U.S. Citizenship and Immigration Services and John Mitnick, the agency’s general counsel — may also depart. And the leadership of Immigration and Customs Enforcement remains in upheaval after Trump last week pulled the nomination of acting director Ronald Vitiello, saying he wanted to go in “a tougher direction.”

The director of the Secret Service, Randolph Alles, whose agency is a unit of DHS, resigned on Monday for unspecified reasons. The White House is discussing a different job for him, perhaps within Customs and Border Protection, where he used to work, according to a senior administration official.

Republicans have expressed alarm at Trump’s purge of DHS, questioning whether the president has a plan to regain control of migration over the border or if he is simply adding to vacancies in the immigration agencies.