They already have. The Jan 6th coup attempt saw mutiple cops killed and dozens seriously injured. Only one traitor was killed by a guard, with several more killed by accidents (like falling off the building as on tried to climb it). Instead of trying to block them in and arresting them, they were all simply let go. Over 2 years later, and only a few hundred have been arrested, all but a handful only sentenced a few weeks.

Moral of the story: if you are going to protest in the US, be clearly armed. Best way to insure peace these days.