Protesters chant 'Lock him up' at Flynn as he leaves courthouse

— -- Echoing Michael Flynn's own calls to imprison Hillary Clinton, a group of protesters threw the former national security advisor's words back at him as he left a Washington D.C. federal courthouse Friday after pleading guilty to lying to the FBI.

“Lock him up, lock him up,” they chanted again and again. On Twitter, Rep. Maxine Waters, D-CA, also joined in.

In July 2016, it was Flynn leading the chants during his speech at the Republican National Convention. “Lock her up, lock her up,” he chanted about Trump’s opponent in the presidential campaign, Hillary Clinton.

On Friday, Flynn pleaded guilty to lying to investigators about the nature of his conversations with then-Russian ambassador to the United States Sergey Kislyak during the presidential transition. The charge carries a sentence of up to five years in prison.

Flynn has promised “full cooperation” in special counsel Robert Mueller’s investigation into possible meddling by Russia in the presidential election.

Flynn served as Trump’s first national security advisor and advised Trump on the campaign as early as January 2016. At one point, ABC News and other outlets reported Flynn was under consideration for vice president.

But less than a month after Flynn was named national security advisor, reports that Flynn lied about his conversations with the Russian ambassador ended his White House career.

Flynn told then-Vice President-elect Mike Pence that the conversations were about “Christmas wishes” and a recent plane crash in Russia, Pence said in a January interview. Published reports said the conversations were about sanctions against Russia imposed by the Obama administration, though Flynn repeatedly denied it.

When the subjects of the multiple conversations Flynn had with the ambassador were revealed, Trump asked for his resignation. Flynn gave it on Feb. 13.

ABC News' Alex Mallin, Jordyn Phelps and Megan Hughes contributed reporting.