Republican Donald Trump on Thursday accused Bill Clinton and Attorney General Loretta Lynch of showing bad judgment by meeting at a time when the former president’s wife, Democratic presidential candidate Hillary, is under federal investigation.

The private meeting took place on Lynch’s plane after she landed in Phoenix on Monday night and Bill Clinton was leaving the airport after a rally he held for his wife earlier that day.

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Hillary Clinton is under an FBI investigation for her use of a private email server when she was President Barack Obama’s first-term secretary of state.

Republican candidate Trump, who was holding a town hall meeting in Manchester, New Hampshire, on Thursday, told conservative radio talk show host Mike Gallagher that the meeting was proof of his charge that the U.S. political system is “rigged” in favor of political elites.

“You see a thing like this. Even in terms of judgment. How bad a judgment is it for him or her to do this. Who would do this?” Trump said.

Lynch, appointed to her position by Obama more than a year ago, said she did not discuss the email investigation or other pending matters before the Justice Department with Bill Clinton.

“When I was landing at the airport, I did see President Clinton at the Phoenix airport as I was leaving and he spoke to myself and my husband on the plane,” Lynch told reporters on Tuesday.

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“Our conversation was a great deal about grandchildren. It was primarily social and about our travels. He mentioned the golf he played in Phoenix and he mentioned travels he had to West Virginia…But there was no discussion of any matter pending for the Department or any matter pending before any other body,” Lynch said.

The Federal Bureau of Investigation is investigating Hillary Clinton about her email use and has already interviewed some of her aides. The investigation into whether laws were broken as a result of the server kept in her New York home has overshadowed Clinton’s campaign.

Obama is preparing to campaign with Hillary Clinton. They are to appear together in Charlotte, North Carolina, next Tuesday.

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At the White House, spokesman Josh Earnest made clear that Obama believes an impartial investigation is crucial and noted that Lynch had said the conversation was benign.

“I think the bottom line is simply that both the president and the attorney general understand how important it is for the Department of Justice to conduct investigations that are free of political interference. And that’s been a bedrock principle of our criminal justice system in this country since our founding. The rule of law is paramount,” Earnest told reporters.

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(Additional reporting by Jeff Mason; Editing by Alistair Bell)