A group of more than a hundred gathered in front of Ann Arbor's Justice Center and City Hall Saturday at 4:30 p.m. to protest Washtenaw County Prosecutor Brian Mackie's decision to not charge police officer David Ried in the fatal shooting of 40-year-old Aura Rosser.

Monique Becker was the first to speak to the crowd through a megaphone outside 301 E. Huron St., which houses City Hall, the 15th District Court and the Ann Arbor Police Department.

"You can pretend that she deserved to die or that her life doesn't matter, so long as you're a cop or a racist ally of this system of oppression," she said. "All lives matter. Black lives matter. Black women's lives matter. Aura Rosser's life matters."

Becker and a group of organizers then took over downtown Ann Arbor streets, disrupting traffic and frustrating some motorists. They carried signs that read: "Black lives matter" and "Prosecute Ried" while shouting chants like, "Show me how democracy works, this is how democracy works!"

The protesters went south on Fifth Avenue to Washington, headed east to State, went south to Liberty, and then went west until they got to Main Street.

At Main Street and Huron, one of downtown Ann Arbor's busiest intersections, the crowd stopped and effectively took it over. Many sat for a moment of silence. Vehicle traffic stopped. Ann Arbor police showed up to help direct traffic, but the protest remained peaceful.

Ann Arbor police said there were no arrests and the demonstration broke up a little after 6 p.m.

Melvin Parson, of Ann Arbor, said the issue of police brutality brought him to the event.

"I would like to assume that the prosecutor's decision was based on sound evidence and not based upon certain systemic influences," he said.

Claire Whitlinger, a sociology graduate student at U-M, said she wasn't quite sure what she felt about the prosecutor's report.

"This is a really complicated issue," she said. "I do know that we really need to fundamentally change the way we do policing. The people being most affected are African Americans and I'm not OK with that."

Rosser was attacking her boyfriend, 54-year-old Victor Stephens, in the hallway of his home at 2083 Winewood Ave. in Ann Arbor around 11:45 p.m. Nov. 9 when police arrived after being called by Stephens, according to a 12-page memo issued by the prosecutor Friday evening.

"After the officers yelled at Ms. Rosser to drop the knife, she came at the officers with the knife still raised in an attack position," Mackie said in a release. "Ms. Rosser ignored repeated commands to drop the knife. As she continued to advance on the officers, Officer Ried fired one shot from his department issued handgun, killing Rosser."

Mackie determined the killing was justified and did not choose to prosecute.

John Counts covers crime and breaking news for The Ann Arbor News. He can be reached at johncounts@mlive.com or you can follow him on Twitter. Find all Washtenaw County crime stories here.