Now, as white-power organizations declare their intentions to rally in cities around the country, police departments are looking to Charlottesville for hints on how to keep the peace — and what mistakes to avoid. Charlottesville, too, is seeking answers. The city announced on Friday that it had hired a former United States attorney to evaluate the planning and response to three white supremacist events in the city this year. The final rally, a show of power by white supremacist groups, was ostensibly held to protest the removal of a statue of Robert E. Lee, the Confederate general.

Officials have insisted that no “stand down” order was issued, and a state police spokeswoman said troopers did not hear the shot. But many people suspect the inaction was deliberate, because just a month earlier, the police were heavily criticized for responding harshly at a Ku Klux Klan rally where anti-Klan protesters were sprayed with tear gas and arrested.

On the day of the “Unite the Right” rally, Aug. 12, only eight arrests were made, even with 125 local officers, hundreds of National Guard troops, the state police and neighboring police agencies present. Those arrested included James A. Fields, the driver who has been charged with murder in the death of Heather D. Heyer.

Investigators are also close to making arrests in the case of DeAndre Harris, 20, a local teacher’s aide and African-American who was beaten with a metal pipe and slabs of wood in a parking garage just a few yards from Police Headquarters, the city manager, Maurice Jones, said.

The police chief and mayor declined requests to be interviewed.

Mr. Jones said the police had developed two “tactical mobile force contingency plans” that were to be used as “quick responders” to skirmishes and fights that were popping up throughout downtown. The officers were instructed to “respond to fights directly” and to make arrests in teams and squads, he said.