- Kirstjen Nielsen is out as secretary of the Department of Homeland Security, President Donald Trump announced Sunday.
- Trump frequently raged against Nielsen for over illegal immigration, and blamed her for the rising number of families apprehended at the US-Mexico border.
- Nielsen has overseen the department amid a number of controversies, most notably the family separations last spring that forcibly pulled thousands of migrant children from their parents.
Kirstjen Nielsen is out as Homeland Security Secretary, President Donald Trump tweeted Sunday, amid ongoing controversy over a surge in Central American asylum-seekers crossing at the US-Mexico border.
"Secretary of Homeland Security Kirstjen Nielsen will be leaving her position, and I would like to thank her for her service," he tweeted.
It's unclear whether Nielsen resigned or was forced out. Trump said Kevin McAleenan, the current US Customs and Border Protection Commissioner, will become acting secretary.
Nielsen's departure is the latest to roil Trump's ever-changing cabinet. The president's frustration with Nielsen's job performance steadily growing throughout last spring and summer, when the number of families apprehended crossing the US-Mexico border began surging.
His anger reached a boiling point last fall as several migrant caravans set out from Central American countries, steadily traveling north in the hopes of reaching the US.
The face of border arrests and family separations
Trump, who frequently uses the monthly border apprehension statistics as a barometer for the effectiveness of his immigration agenda, has largely blamed Nielsen for the uptick, even as she has defended his more controversial policies, including the "zero-tolerance" immigration policy that separated more than 2,500 migrant children from their parents.
Nielsen also drew heavy scorn from Trump critics last June, when she held a combative press briefing at the White House and denied that the Trump administration had created a family-separation policy, even as families were being forcibly separated en masse.
"Why would I ever create a policy that purposely does that?" Nielsen said. "This administration did not create a policy of separating families at the border."
The controversy prompted several Democratic lawmakers to call on Nielsen to resign at the time.
Read more: The Trump administration is reportedly considering a new family separation policy for immigrants
Nielsen's DHS tenure has been dotted with conflict and uncertainty in the months since she was hired to replace John Kelly, her former boss who was hired as the White House chief of staff.
She reportedly drafted a resignation letter in May after Trump berated her in front of cabinet officials and accused her of failing to adequately secure the US's southern border.
Nielsen later addressed the reports by saying Trump was "rightly frustrated" about border security, and that she shared his frustration.
Cracking down at the border
Yet even as she has defended Trump's more controversial policies and statements, Nielsen also reportedly sought to rein him in on some of his wilder proposals.
Nielsen has reportedly complained that Trump and his allies don't understand the nuances of immigration and asylum law, which prevent the federal government from indefinitely detaining migrant children and deporting them and their parents quickly.
Nielsen has also mocked Trump's repeated calls for a border wall, according to The Washington Post, and said privately it's unlikely to ever be built.
When Nielsen recently tried to push back against Trump's calls to close the US-Mexico border entirely, Trump grew impatient and frustrated, aides told The Post in November.
Her apparent skepticism for Trump's most extreme border proposals, combined with her history as a Kelly aide and Bush administration alumna, have prompted Trump to question her loyalty.
According to The Post, Trump calls Nielsen a "Bushie," referring to her past work for President George W. Bush as a special assistant to the president for prevention, preparedness, and response.