The concept of "police" only works where crime is occasional, and the cops can converge lots of men on a localized incident. You will also notice that cops these days will NOT want to show up unless they overwhelmingly outnumber and outgun the bad guys.
When there are more incidents than cops, the system breaks down. Most union, civil service cops these days will find a doughnut shop rather than willingly walk into a situation where there is significant personal danger. Look at New Orleans during Katrina.
Outdated pre-digital age tactics: all based on the simple premise that rioters always eventually settled down, and lined up in front of the local neighborhood welfare offices to receive their payouts in the form of paper checks. All that comes by EBT now. There will be no "settling down." Everbody inside the cordon will be SOL.