I think the solution is as follows, and is fairly simple:
The Ferguson police department and city council announce that for a period of 96 hours, 4 days, there will be zero police nor fire department nor EMT presence and no civil authority of any kind will respond to any 911 call nor request for assistance of any kind. There will be no law enforcement and there will be no prosecution of any crimes committed during this window, no matter how heinous. This happens October 29-30-31-Nov 01, so Halloween and a weekend are in there. It could called the “whoop-ass festival”.
The two days before are intended as days when anyone who wishes not to be present during “whoop-ass” can leave, but equally, anyone who really, really wants to come in and cause trouble can do so.
The three days AFTER whoop-ass NOBODY gets to leave town. This is when the residents or whomever is left in the town can extract revenge against anyone who may have wronged them during whoop-ass. Thus there is a solid 7 days of whoop-ass, whoop-ass week if you will.
Like the movie PURGE ?