Outgoing Department of Homeland Security Secretary Kirstjen Nielsen triggered her own demise by refusing to fire a pair of agency officials that were slow-walking President Trump's immigration agenda, says a former administration official who worked with all three people.

"I think she was an obstructionist to getting rid of the bad people," the official, who asked to speak on background in order to speak openly, said in a phone call with the Washington Examiner Tuesday. The official specially mentioned the department's General Counsel John Mitnick and Citizenship and Immigration Services Director L. Francis Cissna — both of whom have been reported to be next on Trump's chopping block.

Their departures would follow what's already been nearly a week of upheaval at DHS. In addition to getting rid of Nielsen, Trump rescinded the nomination of acting ICE Director Ronald Vitiello and terminated Secret Service Director Randolph Alles from his position.

Mitnick and Cissna are under scrutiny for not aggressively pursuing Trump's approach to stopping illegal immigration along the U.S.-Mexico border. Both are holdovers from the DHS of John Kelly, who headed the department for the Trump administration's first six months or so, before becoming the president's chief of staff.

"When Kelly left, they never took the bad people with them. Everyone makes bad hiring decisions, [but] you don’t leave them on."

The former official named Mitnick as the "reason why most of the immigration policies from DHS never came to fruition."

Mitnick, in particular, is getting blame from Trump allies for details implementing a 2015 court ruling mandating that children who arrive at the border with parents cannot be held more than 20 days in Immigration and Customs Enforcement custody.

A DHS official slammed the allegations.

“Outside voices criticizing the department’s general counsel for working to assiduously to follow the law while implementing the president’s security first agenda likely know little about the law, and less about homeland security , " the official said.

Trump administration officials contend the court ruling is the reason why record-high numbers of Central American families have traveled to and illegally entered the country at the U.S.-Mexico border. That's because DHS lacks the space and legal ability to hold people for the duration of their asylum hearings.

The official said Mitnick's office is sorting through comments and making small changes to the language, but that it should not take two years to do.

"John Mitnick got really good at letting this career and bureaucracy overwhelm him. You need someone that’s going to be a fierce defender of what we’re doing in the Trump administration, not someone who’s gong to let the deep state run everything," the official said.

Cissna, meanwhile, likely hurt his own cause by having his office issue permits for those who illegally entered the U.S. to obtain work documents while they await asylum decisions, 90 percent of which are denied.

"He’s part of the reason we have a flood at the border," the official added.

But the DHS official broke with the rogue official again.

“Director Cissna has restored USCIS’ focus on national security, economic prosperity, and protecting U.S. workers. He has taken numerous steps to end illegal or inappropriate benefit programs and brought integrity to the immigration application process. He has wide support from conservatives on the Hill and in the homeland security community," the DHS official said.

USCIS referred the Washington Examiner to a March list that cites 10 examples of how the agency is "improving the integrity "of the immigration system. The agency's list touted ways it says it has enhanced fraud detection among visa applicants and transparency among employment-based visa applicants."