“If they’ve been doing the same tactics for 100 days and absolutely nothing has changed, you’ve got to change the tactics,” she said, reflecting on the near nightly protests that have taken place here since Mr. Brown was killed on Aug. 9.

Part of the challenge for activists here and across the country is whether they can or want to agree on a concrete agenda, whether it be civilian review boards for police, or special prosecutors, or a push for more minority police officers.

Getting there will also require bridging generational and tactical divides, activists said.

On the one hand, a new crop of young activist groups has brought energy and attention since Mr. Brown’s killing. On the other hand, it is the older, more established civil rights leadership that has the resources and knowledge of how to push concrete measures. Yet some of the younger activists remain skeptical of their older counterparts and of participating in traditional politics. There also remain questions of how militant or peaceful the groups want to be.

“It’s been a little disjointed,” said Alisha Sonnier, 19, the president of Tribe X, a youth activist group in the St. Louis region that formed after Mr. Brown’s death. “At the end of the day all of us are dealing with similar feelings and similar emotions. There’s a disjointment in how we feel we should go about it.”

On Friday afternoon, Ms. Sonnier’s organization led about 100 protesters through the Galleria in suburban Richmond Heights. They chanted and sang for about an hour, adjusting their slogans and lyrics to fit the moment (“Hands up! Don’t shop!” for instance, and “No true bill set our soul on fire,” sung to the tune of “chestnuts roasting on an open fire” from “The Christmas Song.”) Dozens of police and security personnel trailed the protesters but did not make any arrests. Several stores closed before the management eventually closed the entire mall. Similar protests led to closings at two other area malls later Friday.“One of the few ways to be heard and have people listen to you is to have an economic impact,” Ms. Sonnier said. “If you want to really affect people, especially those who are in power, you got to hit their pocket. We as a people cannot allow people to keep making money and a business to go on, and we can’t even get justice when our people die.”

The Rev. Al Sharpton, who was planning to start a countdown to a decision by the grand jury in New York that is looking into the case of Eric Garner, 43, who died after being placed in a chokehold while the police attempted to arrest him for allegedly selling cigarettes illegally on July 17, said he had learned a lesson from the Trayvon Martin case.