uhhhhhhhhhhh it's already happened once before?
https://www.nbcnews.com/politics/politics-news/after-night-significant-damage-d-c-mayor-bowser-imposes-earlier-n1221126
The protesters had expected to have until a 7 p.m. curfew to voice their criticism, but police moved on them almost a half-hour before that. Washington Mayor Muriel Bowser had announced the 7 p.m. curfew earlier Monday, but it was clear shortly after 6 p.m. that authorities were getting ready for imminent conflict.
Attorney General William Barr walked purposefully between lines formed by U.S. Park Police, National Guard members and law enforcement officers from various federal agencies. The officers put on gas masks, raised shields and moved forward until they were face to face with protesters.
Then they backed off a little, and police rushed in from the east side of the street, firing rubber bullets, pepper spray, tear gas and flash-bang grenades into the crowd.