Colin Powell, a retired four-star general who served under three Republican presidents, slammed Donald Trump’s closest military adviser, retired Gen. Michael Flynn, as “right-wing nutty” and “a jerk” according to the former secretary of state’s personal emails seen by BuzzFeed News.

Flynn has been advising Trump and is a close confidant of the Republican nominee. Powell was discussing Flynn, who served as the director of the Defense Intelligence Agency for two years under president Obama with Powell’s son, former FCC chairman Michael Powell. The two Powells were discussing Flynn’s speech to the Republican National Convention, where he led a chant of “lock her up” about Hillary Clinton.

“I spoke at DIA last month,” Powell wrote in a July 19 email exchange with his son. “Flynn got fired as head of DIA. His replacement is a black Marine 3-star. I asked why Flynn got fired. Abusive with staff, didn’t listen, worked against policy, bad management, etc. He has been and was right-wing nutty every [sic] since. I watched about five minutes on line of his talked [sic] and switched off.”

The Washington Post reported when Flynn was forced out of the DIA that “critics said that his management style could be chaotic,” and he clashed with other senior intelligence officials. Flynn, when was being vetted as a possible vice presidential candidate for Trump, wrote in the New York Post that the “military fired me for calling our enemies radical jihadis." In a profile of Flynn last month, the Washington Post spoke to a former senior U.S. intelligence official who disputed Flynn’s characterization of his firing, saying it was “about turbulence and a destructive climate” during his tenure.

“Thought it was disgraceful to see a military officer leading chants for a putative President of the United States to be ‘locked up,’” Michael Powell wrote back to his father.

“Pattern of behavior which is why he was fired, real question is how he got that far in the Army,” Powell wrote back. “Found no coverage of his remarks.”

“No surprise, the performance was really terrible. He bumbled, message incoherent and shrill,” Michael Powell said.

The website DCLeaks.com — which has reported, but not confirmed, ties to Russian intelligence services — obtained Powell’s emails. It may be the latest example of a Russian entity potentially trying to influence the US presidential election — in July, the FBI said it believed Russia was behind the hack of the Democratic National Committee’s internal emails right before the party’s convention.

Powell declined to comment on the emails to BuzzFeed News.

In another exchange in early August with Harlan Ullman, the chairman of the Killowen Group, Powell again showed his disdain for Flynn.

“Gen. Flynn is a jerk. Got canned out of DIA,” wrote Powell.

“Trump has Trumped himself. I thought he was merely dyslexic and narcissistic. I now believe he is mentally unbalanced and quite possibly deranged,” Ullman wrote to Powell in the same exchange.

“No question about it. Still nutty statements as of yesterday,” Powell wrote back.

Similarly, Powell panned Flynn’s performance in an interview with Al-Jazeera English in an early August exchange with a Reuters reporter.

“I watched an Al Jaz reporter eat Flynn’s lunch for almost ten minutes. He had done his homework,” he said.

In a mid-August exchange with a Reuters reporter, Powell was more diplomatic on Flynn, speaking as an unnamed official.

“I never knew or served with Flynn,” wrote Powell. “You know how long I have been out. [He] came to my attention by some rather drastic changes he was trying to impose on DIA operations. He was either eased out or fired. I hear two different stories. Talking to people in the know his real problem was leadership and management issues at DIA. Senior staff was in incipient revolt,” he wrote.