Washington(CNN) Two senior Department of Homeland Security officials have been forced to resign by the White House, according to sources familiar with the resignations.
Among them was a top official in DHS's cyber arm, who resigned amid a national security shakeup by the Trump administration. Bryan Ware served as assistant director for cybersecurity at DHS' Cybersecurity and Infrastructure Security Agency (CISA).
DHS assistant secretary for international affairs Valerie Boyd also resigned amid pressure from the White House, officials tell CNN.
DHS, CISA and the White House declined to comment on the resignations.
Ware's resignation letter, seen by CNN, is addressed to President Donald Trump and says his resignation is effective Friday. In it, he writes that it has been an honor to serve, highlighting his work on election security and the Covid-19 response.
But his farewell letter to staff indicates that he did not want to step down. He says that he is leaving "with much sadness" and that "it's too soon." He went on to list their accomplishments during his tenure. "We secured election day from foreign interference. Boom!" he wrote of his resignation, which was first reported by CyberScoop.
In a letter to the workforce, CISA Director Christopher Krebs praised Ware's efforts on election security, defense of federal networks and work on defending healthcare systems.
"Bryan approached each new challenge with enthusiasm and a collaborative attitude, helping to drive forward changes necessary to mature CISA as an operational Agency" Krebs wrote.
Matt Hartman -- Ware's deputy -- will step into role of acting assistant director, according to Krebs' announcement.
The resignations come in the wake of sweeping changes atop the Defense Department's civilian leadership structure which has seen several of the Pentagon's most senior civilian officials replaced with perceived loyalists to the President. The changes started with Trump firing Defense Secretary Mark Esper on Monday and senior Pentagon officials have told CNN they are alarmed and concerned about what might happen next.
Boyd submitted her resignation on Thursday to acting Homeland Security Secretary Chad Wolf, writing that it is "with sadness that I submit my resignation, effective November 13, 2020."
"It has been my belief that people of character should support the institution of the Presidency and work within it to inform and influence policy decisions that reflect well on the people's government. This belief has been tested many times these past few years, and it is my fervent prayer that I made the best possible choices. I wish you and our colleagues across the government the strength to act with honor in the months ahead," she wrote.
Leadership at the department has been unstable throughout Trump's presidency. DHS—the third-largest federal department—has had five secretaries, only two of whom have been confirmed by the Senate: John Kelly and Kirstjen Nielsen.