Former Chief of Staff John Kelly explained his problems with President Donald Trump at a paid event Wednesday night at Drew University in New Jersey.

He admitted he clashed with the president on several issues while working as chief of staff, including his language regarding illegal immigration and foreign policy.

While he helped facilitate the construction of Trump’s border wall and decrease illegal immigration, he disagreed with the president’s characterization of illegal migrants.

“They’re overwhelmingly good people … They’re not all rapists and they’re not all murderers,” Kelly said. “And it’s wrong to characterize them that way. I disagreed with the president a number of times.”

He also argued that Trump’s efforts to befriend North Korean leader Kim Jong Un and convince him to denuclearize were futile.

“He will never give his nuclear weapons up,” Kelly said. “Again, President Trump tried … that’s one way to put it. But it didn’t work. I’m an optimist most of the time, but I’m also a realist, and I never did think Kim would do anything other than play us for a while, and he did that fairly effectively.”

He then defended Lt. Col Alexander Vindman, who was fired last week in response to him testifying against Trump during the House’s impeachment hearings.

“He did exactly what we teach them to do from cradle to grave,” Kelly told the audience. “He went and told his boss what he just heard.”

Kelly said that Vindman viewed Trump telling the president of Ukraine to investigate a political as “an illegal order.”

“We teach them, ‘Don’t follow an illegal order. And if you’re ever given one, you’ll raise it to whoever gives it to you that this is an illegal order, and then tell your boss,’” he said in defense of Vindman.

Kelly left his post in December 2018, having served just over a year in the role.

“I’m disappointed in myself for leaving, but it was a killer, I mean, no joke,” Kelly said Wednesday.