US Secretary of the Army Ryan McCarthy told reporters on Friday that the crew of a National Guard helicopter had been grounded pending the outcome of a 15-6 investigation into an incident in Washington, DC, earlier this week. He said he could not disclose further information about the chain of command above the crew, due to the nature of the probe.
After the 7 p.m. curfew came and went on Monday, thousands of protesters across the nation's capital were driven from the streets by a bevy of city and federal police, as well as units of the city's National Guard and guardsmen from other states. In one incident captured by multiple reporters and onlookers, helicopters descended below rooftop level to hover just yards above protesters' heads in an effort to intimidate them into leaving.
At least two incidents were reported: one on Judiciary Square, next to several courthouses, and another in Chinatown, and onlookers noted both UH-72 Lakota and UH-60 Black Hawk helicopters were involved. However, McCarthy reportedly only mentioned the Lakota crew.
Extremely low. Looked like NG manned but I'm not an expert obviously. Definitely blew a few people over in the wash. pic.twitter.com/MRjs2NB2Ud
— Sam Ward (@LiveByTheSWard) June 2, 2020
In DC, @MaxBlumenthal (https://t.co/OZ6aBZpZGK) films a US helicopter hovering low to the ground over a group of protesters. pic.twitter.com/Blf15KLkIt
— Aaron Maté (@aaronjmate) June 2, 2020

The rotor wash knocked people over and snapped tree limbs in nearby parks.
After footage of the chopper went viral, DC National Guard commander Maj. Gen. William J. Walker announced he would open an investigation into the incident.