Introduce them to CPD’s 12 guage riot shotguns. Three quick rounds of buckshot will clear them out. No mercy necessary.
A squadron of police armed with street sweepers would clear the streets in no time.
(A street sweeper is a 12 gauge shotgun with a 30 round drum magazine; very useful for trash cleanup.)
If I’m not mistaken, the street sweeper magazine is loaded with 30 rounds of OO buckshot.
Somewhat messy but sends a very effective message.