In an extraordinary rebuke, former defense secretary Jim Mattis on Wednesday denounced President Donald Trump’s heavy-handed use of military force to quell protests near the White House and said his former boss was setting up a “false conflict” between the military and civilian society.

“I have watched this week’s unfolding events, angry and appalled,” Mattis wrote.

The criticism was all the more remarkable because Mattis has generally kept a low profile since retiring as defense secretary in December 2018 to protest Trump’s Syria policy. He had declined to speak out against Trump, saying he owed the nation public silence while his former boss remained in office.

But he’s speaking out after this past week’s protests in response to the death of George Floyd in police custody.

Mattis had a scathing description of Trump’s walk to a historic nearby church Monday to pose with a Bible after law enforcement forcibly cleared Lafayette Square of mostly peaceful protesters.

He said he never dreamed troops “would be ordered under any circumstance to violate the Constitutional rights of their fellow citizens — much less to provide a bizarre photo op for the elected commander-in-chief, with military leadership standing alongside.”

“Donald Trump is the first president in my lifetime who does not try to unite the American people —does not even pretend to try. Instead he tries to divide us,” Mattis wrote in a statement published by The Atlantic. “We are witnessing the consequences of three years of this deliberate effort. We are witnessing the consequences of three years without mature leadership.”

Mattis called on Americans to unite without Trump. “This will not be easy, as the past few days have shown, but we owe it to our fellow citizens; to past generations that bled to defend our promise; and to our children,” he wrote.

Mattis said of the protesters that Americans should not be distracted by a small number of lawbreakers. He said they are rightly demanding that the country follow the words of “Equal Justice Under Law” that are on display at the U.S. Supreme Court.

“The protests are defined by tens of thousands of people of conscience who are insisting that we live up to our values — our values as people and our values as a nation,” Mattis said.

Mattis took particular issue with the use of force to move back protesters so Trump could visit St. John’s Church the day after it was damaged by fire during protests.

“We know that we are better than the abuse of executive authority that we witnessed in Lafayette Square. We must reject and hold accountable those in office who would make a mockery of our Constitution,” Mattis said.

One day after Trump announced he was pulling all U.S. troops out of Syria, where they were partnering with local Syrians to fight the Islamic State, Mattis tried but failed to change Trump’s mind. So, he resigned. Trump soon turned on Mattis, calling him a failure. He said falsely that he had fired Mattis.

“What’s he done for me?” Trump said January 2. “How had he done in Afghanistan? Not too good. I’m not happy with what he’s done in Afghanistan, and I shouldn’t be happy.”