Hours before law enforcement forcibly cleared protesters from Lafayette Square in early June amid protests over the police killing of George Floyd, federal officials began to stockpile ammunition and seek devices that could emit deafening sounds and make anyone within range feel as if their skin was on fire, according to an Army National Guard major who was there.

D.C. National Guard Maj. Adam D. DeMarco told lawmakers that defense officials were searching for crowd-control technology deemed too unpredictable to use in war zones and had authorized the transfer of about 7,000 rounds of ammunition to the D.C. Armory as protests against police use of force and racial injustice roiled Washington.

In sworn testimony, shared this week with The Washington Post, DeMarco provided his account as part of an ongoing investigation into law enforcement and military officers’ use of force against D.C. protesters.

President Trump on June 1 visited the historic St. John’s Episcopal Church, which was damaged by protests in Washington, D.C. (The Washington Post)

On June 1, federal forces pushed protesters from the park across from the White House by blanketing the street with clouds of tear gas, firing stun grenades, setting off smoke bombs and shoving demonstrators with shields and batons, eliciting criticism that the response was extreme. The Trump administration has argued that officers were responding to violent protesters who had been igniting fireworks, setting fires and throwing water bottles and rocks at police.

But DeMarco’s account contradicts the administration’s claims that protesters were violent, that tear gas was never used and that demonstrators were given ample warning to disperse — a legal requirement before police move to clear a crowd. His testimony also offers a glimpse into the equipment and weaponry federal forces had — and that they sought — during the early days of protests that have continued for more than 100 days in the nation’s capital.

DeMarco, who provided his account as a whistleblower, was the senior-most D.C. National Guard officer on the ground that day and served as a liaison between the National Guard and U.S. Park Police.

The chaos that erupted on the evening of June 1 played out before millions of viewers on split-screen television broadcasts as President Trump strode through the emptied park toward St. John’s Episcopal Church, where he delivered remarks and posed for photos with a Bible.

U.S. Park Police Chief Gregory Monahan has testified that protesters were given clear warnings to disperse via a Long Range Acoustic Device. But DeMarco told lawmakers that is impossible because there was no such device on the scene at the time.

Just before noon on June 1, the Defense Department’s top military police officer in the Washington region sent an email to officers in the D.C. National Guard. It asked whether the unit had a Long Range Acoustic Device, also known as an LRAD, or a microwave-like weapon called the Active Denial System, which was designed by the military to make people feel as if their skin is burning when in range of its invisible rays.

Col. Robert Phillips of the Defense Department’s Joint Forces Headquarters-National Capital Region said in a statement Thursday that the officer sent the email — which DeMarco cited in his testimony — “as a matter of due diligence and prudent military planning” to determine what capacity agencies had “across the full spectrum of non-lethal systems.” He said “JFHQ-NCR does not possess these systems, did not request such systems, and no further action was taken” after the email was sent.

The Defense Department, U.S. Army and D.C. National Guard did not respond to specific questions about munitions and their intended use.

The Active Denial System, also called a “heat ray,” was developed to disperse large crowds in the early 2000s but was shelved amid concerns about its effectiveness, its safety and the ethics of using it on human beings.

Pentagon officials were reluctant to use the device in Iraq. In late 2018, the New York Times reported, the Trump administration had weighed using the device on migrants at the U.S.-Mexico border — an idea shot down by Kirstjen Nielsen, then the Homeland Security secretary, citing humanitarian concerns.

Ethical and safety concerns have long shadowed the device. When it first debuted in 2001, Human Rights Watch adviser William M. Arkin wondered how it might affect children or pregnant women who happened to be in a crowd.

The burning effect comes from a gyrotron, which creates heat by pushing energy through a magnetic field, similar to a microwave. The weapon generates millimeter waves meant to penetrate 1/64th of an inch into the skin — enough to hurt without leaving burns. But in a 2007 military test, a change in the device’s power settings resulted in second-degree burns to one airman’s body.

The military spent millions developing and testing the device, zapping thousands of military volunteers. Yet, when the first serious demand came to deploy it in combat during the Iraq War, military leaders demurred. Though the heat ray was actually shipped to Afghanistan in 2010, it was recalled within weeks and never used.

But in the email, on which DeMarco was copied, the lead military police officer in the National Capital Region wrote that the ADS device “can provide our troops a capacity they currently do not have, the ability to reach out and engage potential adversaries at distances well beyond small arms range, and in a safe, effective, and nonlethal manner.”

The email continued: “The ADS can immediately compel an individual to cease threatening behavior or depart through application of a directed energy beam that provides a sensation of intense heat on the surface of the skin. The effect is overwhelming, causing an immediate repel response by the targeted individual.”

Federal police ultimately were unable to obtain a heat ray device — or an LRAD — during the early days of protests in D.C., according to the Defense Department official.

DeMarco said that without an LRAD device, which can be used to make booming announcements to large crowds, Park Police officers instead issued dispersal orders to the crowd using a handheld red-and-white megaphone.

Laws and court rulings require police to give demonstrators repeated, clear warnings of officers’ intentions to escalate and to allow people adequate time and avenues to disperse peacefully.

DeMarco told lawmakers he was standing about 30 yards from the announcer but could barely make out the order. The chanting crowd, which was even farther from the officer with the megaphone, did not appear to hear the warnings, DeMarco said.

Protesters, journalists and humanitarian aid volunteers who were there that day have repeatedly said they never heard a warning before police began to move on the crowd. Advancing on foot and horseback, they pushed protesters back as explosions sent clouds of smoke and chemicals into the air, and officers fired rubber pellets into groups of retreating protesters.

Monahan has said violence by protesters spurred his agency to clear the area ahead of the D.C. mayor’s 7 p.m. curfew — instituted as a response to looting, vandalism and arson amid demonstrations on previous nights — with unusually aggressive tactics.

Monahan also told members of Congress in July that Park Police had followed protocol in issuing three warnings “utilizing a Long Range Acoustic Device” — although DeMarco’s testimony indicates no such device was in use.

U.S. Park Police did not respond to a request for further comment this week.

DeMarco first appeared before lawmakers on the House Natural Resources Committee in late July but followed up at the end of August with more specific answers to legislators’ questions about munitions and equipment used by law enforcement. His answers, submitted in written form, were shared with The Post this week by congressional staff of the Natural Resources Committee.

De Marco told lawmakers he felt compelled to come forward as a witness because he found the events at Lafayette Square “deeply disturbing.” His attorney, David Laufman, said DeMarco hopes lawmakers will continue to investigate the federal response.

“That anyone in the Department of Defense referred to American citizens exercising their First Amendment rights as ‘potential adversaries’ and even contemplated the use of an ADS on the streets of our nation’s capital is deeply disturbing and calls for further investigation,” Laufman said.

DeMarco also testified that a stash of M4 carbine assault rifles was transferred from Fort Belvoir to the D.C. Armory on June 1 and that transfers of ammunition from states such as Missouri and Tennessee arrived in subsequent days.

By mid-June, about 7,000 rounds of 5.56mm and 7.62mm ammunition rounds had been transferred to the D.C. Armory, DeMarco said.

He did not specify what the ammunition was for, and the D.C. National Guard did not respond to questions about the weapons transfers.

In late June, Congress opened an investigation into tactics used by federal law enforcement officers to clear protesters in and around Lafayette Square.

Monahan and DeMarco testified on the same day in July, at which time Monahan said the area around Lafayette Square was cleared June 1 so construction crews could erect a taller fence than the temporary barricades that had closed off the area. The action followed a night in which a Park Service building was set on fire.

DeMarco told legislators that, having served in a combat zone where he spent time assessing various threats, he did not feel threatened at any point by protesters near the White House “or assess them to be violent.”

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

Tim Elfrink contributed to this report.