Army National Guard commander Adam DeMarco will testify on Tuesday that Park Police's use of force in the clearing of Lafayette Square last month was an "unnecessary" and "unprovoked" escalation that he and his fellow National Guardsman viewed as "deeply disturbing."

Why it matters: DeMarco's testimony, previewed in a written statement released by the House Natural Resources Committee on Monday, contradicts statements made by Attorney General Bill Barr and the Trump administration about the controversial clearing of protesters, which preceded President Trump's visit to St. John's Church for a photo op.

The big picture: Barr claims that there was "no correlation" between his decision to clear the park and Trump's visit to the church. He has accused the media of lying about the protesters outside of the White House being peaceful and denied that tear gas was used.

• But DeMarco testified that the protesters "were behaving peacefully" from what he could observe, and that the "irritation" he felt from smoke canisters was consistent with the effects of tear gas, which he has been exposed to during Army training.
• DeMarco also testified that he discovered "spent tear gas canisters" later that evening on the street nearby. A spokesman for Park Police has said it was a "mistake" for the agency to deny that tear gas was used.

What DeMarco is saying:

• "The events I witnessed at Lafayette Square on the evening of June 1 were deeply disturbing to me, and to fellow National Guardsmen. Having served in a combat zone, and understanding how to assess threat environments, at no time did I feel threatened by the protestors or assess them to be violent."
• "It was my observation that the use of force against demonstrators in the clearing operation was an unnecessary escalation of the use of force. 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."
• "As the late Representative John Lewis said, 'When you see something that is not right, not just, not fair, you have a moral obligation to say something, to do something.'"

Read the full statement.