A senior officer in the D.C. National Guard deployed to Lafayette Square during a contentious night of protests on June 1 says U.S. Park Police used tear gas and other unnecessary, forceful tactics to disperse peaceful demonstrators.

Major Adam DeMarco will testify Tuesday in front of members of Congress as part of the House Natural Resources Committee’s second hearing on the events of that night.

“When you see something that is not right, not just, not fair, you have a moral obligation to say something, to do something,” DeMarco says in his written testimony, published today. The line is a quote from the late Congressman John Lewis.

The acting chief of the U.S. Park Police, Gregory T. Monahan, will also testify at Tuesday’s hearing. Monahan was invited to the first hearing on June 29 but said he was not available.

DeMarco says he was activated by the D.C. National Guard to help respond to a wave of local protests following the deaths of George Floyd, Breonna Taylor, and other Black people killed at the hands of police. On the night of the protest in question, DeMarco was working as a liaison between the D.C. National Guard’s civil disturbance task force and the U.S. Park Police.

In a briefing, DeMarco learned the Park Police and Secret Service planned to clear protesters from H Street NW (which borders the north end of Lafayette Square) and establish a new security perimeter on I Street NW.

Around 6 p.m., an hour before the city’s curfew was scheduled to start, DeMarco says he was standing in the middle of Lafayette Square watching demonstrators “behaving peacefully, exercising their First Amendment rights.”

Around that time, DeMarco saw Attorney General William Barr and General Mark Milley, the Chairman of the Joint Chiefs of Staff, walking across Lafayette Square from the White House. Milley asked DeMarco for a briefing before asking him to keep National Guard personnel calm and to respect the demonstrators’ rights.

About 20 minutes later, after Barr and Milley left Lafayette Square, DeMarco says he heard Park Police issue three announcements directing demonstrators to disperse.

Two things struck DeMarco as odd. First, he says he was surprised the announcements were being issued 40 minutes before the 7 p.m. curfew. Second, he worried the protesters couldn’t hear the warnings, which he described as “barely audible.”

“I saw no indication that the demonstrators were cognizant of the warnings to disperse,” he says.

The Park Police and Secret Service began clearing the area 10 minutes later, around 6:30 p.m.

Contrary to what acting chief Monahan would later claim, DeMarco says he believes Park Police did use tear gas on protesters. (He says he felt eye and nose irritation consistent with his previous experiences with tear gas. He also found used tear gas canisters on the street later on in the night.)

“From my vantage point, I saw demonstrators scattering and fleeing as the Civil Disturbance Unit charged toward them,” DeMarco says in the statement.

DeMarco says he saw Park Police “using their shields offensively as weapons,” and unidentified law enforcement agents using “‘paintball-like’ weapons” to shoot pepper balls into the crowd.

After clearing Vermont and Connecticut avenues and 16th Street, DeMarco says he stood on 16th Street between St. John’s Church and the AFL-CIO building. A few minutes later, after 7 p.m., he says he was surprised to see President Donald Trump walk onto H Street from Lafayette Square. Trump then posed for photos while holding a Bible in front of St. John’s Church. DeMarco says he was never briefed on this part of the evening’s plans.

Milley later said he regretted joining Trump on the walk through Lafayette Square that ended in the photo op, saying his presence there created a perception that the military is involved in domestic politics. The National Guard has struggled to appear apolitical under the Trump administration and its controversial role in recent protests has drawn the attention of the Pentagon, which plans to investigate the June 1 incident.

DeMarco says in his testimony he and other National Guardsmen were deeply disturbed by how demonstrators were treated while trying to protest peacefully. Interior Secretary David Bernhardt and some Republican lawmakers dispute the claim that the protesters were uniformly peaceful.

“From my observation, those demonstrators–our fellow American citizens–were engaged in the peaceful expression of their First Amendment rights. Yet they were subjected to an unprovoked escalation and excessive use of force,” DeMarco says.

Oct. 26: The story was updated to clarify when DeMarco was activated.