Former Attorney General Eric Holder on Friday encouraged the "career men and women" at the Justice Department and FBI to "be strong" while they work in the Trump administration.

"Your actions and integrity will be unfairly questioned," he said on Twitter. "Be prepared, be strong. Duty. Honor. Country."

To the career men & women at DOJ/FBI: your actions and integrity will be unfairly questioned. Be prepared, be strong. Duty. Honor. Country. — Eric Holder (@EricHolder) June 30, 2017

The 3 a.m. tweet came as the FBI conducts an independent investigation into Russian meddling in the 2016 presidential election and possible collusion with President Trump's campaign. That investigation is being led by special counsel Robert Mueller.

Holder said something similar he night FBI Director James Comey was fired in May.

"To the career men and women at DOJ/FBI: you know what the job entails and how to do it. Be strong and unafraid. Duty. Honor. Country," he tweeted on May 10, 2017.