WASHINGTON (AP) — The National Guard of the District of Columbia is investigating the use of one of its helicopters to make a "show of force" against protesters near the White House, while President Donald Trump is encouraging authorities to get tougher to quell the unrest over George Floyd's death.

The helicopter, normally designated for use in medical evacuations, hovered low enough to create a deafening noise and spray protesters with rotor wash on Monday. The commanding general of the D.C. Guard, Maj. Gen. William Walker, said in a statement Wednesday that he directed the investigation, and officials

The investigation comes as the federal government has promised to maximize its law enforcement presence in the nation's capital. Scores of heavily-armed federal officers in tactical gear have been on the district's streets for days, after demonstrators set fires, broke store windows and stole items from the shelves and left police officers injured.

The Trump administration has made an effort to show a use of force in Washington. Hours before a 7 p.m. curfew on Tuesday, cars were being stopped at military checkpoints downtown, and a cavalry of armored military vehicles could be seen driving through the district.

Mayor Muriel Bowser said the administration had floated the idea of taking over the Metropolitan Police Department, a proposal she strongly rejected. She threatened to take legal action if the federal government attempted to do so.

Two Defense Department officials said the administration had ordered military aircraft to fly above Washington on Monday night as a "show of force" against demonstrators. They were protesting the death of Floyd, a black man who died after a white Minneapolis policeman pressed his knee into his neck for several minutes even after Floyd stopped moving and pleading for air. Police made over 300 arrests, mainly for violating the district's curfew.

Earlier Monday evening, law enforcement officers on foot and horseback moved aggressively to clear protesters away from Lafayette Park near the White House before President Donald Trump walked to a nearby church for a photo opportunity.

After participating in the show of force, Arlington County in Virginia pulled out its officers, saying they were used "for a purpose not worthy of our mutual aid obligations." County officials said in a statement their officers never wielded their batons and did not fire rubber bullets or tear gas.

After watching the scene unfold on live television, the police chief ordered all the officers to return to Virginia. Officials said they were reevaluating the mutual aid agreements to ensure officers "are never again put in a situation where they are asked to take action that is inconsistent with our values."

The U.S. Park Police said it gave three warnings over a loudspeaker before clearing the area of protesters, some of whom authorities said were becoming violent, throwing projectiles and trying to grab weapons. The agency said it used smoke canisters and pepper balls to disperse the crowd.

Attorney General William Barr ordered law enforcement to clear the park and push back the perimeter around the White House when he arrived there Monday evening, before the president's remarks, and that led to police using force to disperse protesters, a person familiar with the matter told The Associated Press.

Officials had decided the perimeter had to be moved by at least one full block, after fires were set in the park the night before, the person said. When Barr arrived, he was surprised it hadn't been done and directed action to be taken, according to the person, who was not authorized to discuss the matter publicly and spoke on condition of anonymity.

In a Monday call with governors, Trump and Barr encouraged more aggressive action against those who cause violence during protests. Trump said he was "taking immediate presidential action to stop the violence and restore security and safety in America."

The president urged governors to deploy the National Guard, which he credited with helping calm the situation Sunday night in Minneapolis, and demanded that similarly tough measures be taken in cities that also experienced spasms of violence, including New York, Philadelphia and Los Angeles.

Between the protests and the response to the coronavirus pandemic, the National Guard has been deployed at its highest level in recent history, surpassing the number of troops sent to the Gulf Coast during Hurricane Katrina in 2005. More than 66,700 soldiers and airmen have been activated — 45,000 to assist with the pandemic and more than 17,000 to help with the protests.

The Justice Department had deployed agents from every one of its agencies, including the FBI's Hostage Rescue Team, an elite tactical unit, and riot teams from the Bureau of Prisons.

The Park Police and Secret Service have had dozens of officers out in riot gear in Washington for the last few nights, in addition to the Metropolitan Police Department. U.S. Customs and Border Protection and other Homeland Security agencies were also dispatched.

Most of the protesters have been peaceful and tried to discourage violence. Trump, Barr and others have tried to blame some of the civil unrest on left-wing extremist groups, including antifa, and other "anarchists." Short for anti-fascists, antifa is an umbrella term for far-left-leaning militant groups that resist neo-Nazis and white supremacists at demonstrations.

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Associated Press writers Zeke Miller, Lolita C. Baldor and Ashraf Khalil in Washington; James LaPorta in Delray Beach, Florida; and Sarah Blake Morgan in West Jefferson, North Carolina, contributed to this report.