Groups are divided by aim and by geography, with goals of justice for Mr. Brown or an end to lethal police force against minorities, but the path for achieving them is neither clear nor easy.

Certainly there is an array of new coalitions with names like Lost Voices and Tribe X, and across the country this week there were calls to hold police departments accountable and increase social media organizing campaigns. Many of the demonstrations had a distinctly local flavor…

The violence fulfilled the worst fears of Patricia Bynes, a Democratic committeewoman here. Until recently, she was one of the people standing between the police line and the protesters, urging calm on both sides. After the August shooting, she used to try to broker deals for the demonstrators on the front lines. She has since pulled back, saying that lawless actors have hurt the peaceful movement.

She became turned off, she said, several weeks ago after she called out several activists at a protest planning meeting who she said attacked a young man they accused of live-streaming the private session. At a protest a few days later, several members of the group she had criticized surrounded her and threatened her, she said. Only four people came to her defense when they circled her, she said.