"How could Browny be riding his bicycle, struggling with officers, and pull a gun at the same time?" Free the Streets said in a news release.
The protesters said about 80 people turned out Friday night to question the shooting, only to be dispersed by police.
On Sunday night, they described the shooting as "an execution," saying witnesses saw "one officer ordering another to finish him off as he lay wounded and handcuffed on the ground."
The department's Internal Affairs Bureau is investigating the Nov. 11 shooting. Members of Flynn's family said they had not yet been contacted by Internal Affairs investigators.
At Sunday night's protest, a handful of demonstrators, including several of Flynn's relatives, briefly held up traffic on Market Street in West Philadelphia before marching to 19th District headquarters at 61st Street and Haverford Avenue. About 15 people participated in the rally.
They chanted "No justice, no peace!" and "Unite the block - no more cops!" as they marched. Many expressed frustration with police in Philadelphia, calling the department corrupt.
The protesters are demanding that the department identify the officers and release the incident report and autopsy and forensic records.
Arturo Castillon, a spokesman for Free the Streets, which helped organize the protest, said the organization had not yet submitted a formal records request. Records typically are not released during an active investigation.
"Our strategy is more based on putting pressure on the 19th District" through rallies and street protests, "more than just waiting for the legal outcome," Castillon said.
Outside the 19th District station, protesters met with about a half-dozen uniformed officers on hand.
"We're sorry about your brother, but things happen," said Capt. Joseph Bologna, the 19th District's commanding officer, as Flynn's sister, Tasha Flynn, confronted him outside the station.
He told protesters that he understood they were grieving the loss of their relative but that answers to their questions might not be available.
"I know you're hurting, but at this point, it's being investigated," he said. "Everything I know now I'm telling you."
Bologna said the officer who shot Flynn had been taken off the street until the investigation is over.
Lt. Joseph O'Brien said protesters should consult Internal Affairs or the District Attorney's Office for information on the shooting.
Flynn had a long rap sheet, with convictions for drug possession, robbery, assault, theft, and weapons violations dating to 1995. Police called him a violent drug dealer.
Tasha Flynn described her brother as a humble man who "wasn't out here trying to rob or kill nobody."
"My brother would not pull a gun on a police officer," she said. "He knew the repercussions."
She said Flynn didn't have children but enjoyed spending time with youths in the neighborhood, buying juice and snacks for them at the corner store.
The family, Tasha Flynn said, is in shock over his death.
"We are all numb," she said. "We can't believe that it's real. We're not going to accept it, and we're not going to let it go."
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