Former federal prosecutor Glenn Kirschner said he got “patriotic goosebumps” watching disgraced national security adviser Michael Flynn’s demeanor change under harsh rebukes from Judge Emmet Sullivan.

The former assistant U.S. Attorney told MSNBC’s “Morning Joe” he believed special counsel Robert Mueller would “seriously consider” indicting President Donald Trump if evidence showed he broke the law with Flynn’s help to become president.

“You can’t steal the presidency and hold up the presidency as a shield against being held accountable for stealing the presidency,” Kirschner said.

Kirschner said he considered the federal judge a “hero” after sitting in the courtroom during Flynn’s aborted sentencing hearing.

“The first note I took when I was sitting in the courtroom is that the atmosphere seemed lighthearted, more appropriate to a cocktail party than a serious sentencing,” Kirschner said, “but, you know, the whole atmosphere changed and the dark clouds rolled in when it was clear that Judge Emmet Sullivan would not stand for this sort of egregious governmental misconduct.”

Flynn had come in looking confident, but he said the retired U.S. Army general appeared caught off guard by Sullivan’s comments.

“Gen. Flynn’s demeanor changed,” he added. “He went from smiling to smirking, to looking fearful when he ultimately took the judge up on his offer to delay his sentencing.”

Kirschner said the hearing was oddly inspiring.

“I’ve been in those courtrooms for 30 years,” he said, “but I was getting patriotic goosebumps as I heard Judge Sullivan sort of appropriately beat up on Gen. Flynn, and I can tell you, usually Judge Sullivan is one to beat up on the prosecutors. If we’re in there doing something, and I’ve appeared before him, we’re doing something not to his liking, not quickly or efficiently enough, believe me, we are going to hear about it.”

“Yesterday Gen. Flynn was government misconduct personified, and I think that’s why Judge Sullivan focused on him,” Kirschner added.