Chaos in Minneapolis.

Heaping furious, violent contempt on an 8 p.m. curfew declaration and widespread passionate pleas for forbearance and peace, defiant rioters rampaged across Minneapolis for a fourth night Friday and into early Saturday, creating unprecedented havoc as they set towering fires, looted and vandalized businesses and shot at police officers, all in response to the death of an unarmed black man under a white police officer’s knee on Monday.

By all accounts, law enforcement presence was almost undetectable as the violence rapidly accelerated until just before midnight and into early Saturday, when hundreds of police officers, state troopers and National Guard troops, some in armored vehicles, fanned out into troubled areas, confronting rioters with mass force, tear gas and orders to disperse issued via bullhorn.

And yet, those efforts had visibly little impact for much of the night, and questions swirled among citizens and politicians about how such a dire situation could have developed in a long peaceable, progressive city.