For the dozens of protesters who descended on the working-class South Carolina city of North Charleston on Wednesday, a bystander's video of a white police officer gunning down a fleeing black man was long-awaited confirmation of what many residents have been saying for years.

Activists said the footage, showing Officer Michael Slager shooting 50-year-old Walter Scott in the back, is chilling evidence of what they portray as "an atmosphere of racism" that allows African-Americans to be targeted in North Charleston and across the state.

"This is not an isolated incident," said Muhiyidin Moye D'Baha, an organizer with the activist group Black Lives Matter. "This is something that exists within a system down here."

It is a point of view that has been echoed in predominantly African-American neighborhoods across the country, where the more aggressive tactics police have employed to curb crime have stirred deep resentment.

Residents of the St. Louis suburb of Ferguson, Missouri, where an unarmed black teenager was shot to death last summer, described a similar pattern of racial harassment by a mostly white law enforcement establishment.

Local, state and federal officials were quick to condemn the actions by Slager, 33, who was arrested on a murder charge on Tuesday after a witness came forward with video of the Saturday shooting.

In the footage, Scott can be seen running from Slager as the patrolman aims his weapon and begins firing. It was the 11th time this year an officer has been involved in a shooting in South Carolina.

Slager's arrest and termination did little to ease long-simmering racial tensions in the city, where nearly half the residents are black and about 21 percent of the police force is African-American. The police chief and mayor are also white.

Otha Meadows, president of the local chapter of the Urban League and a resident of the city for nine years, said the community was frustrated by a number of shootings of black men by police officers in the region.

"The community has felt that those shootings have gone on deaf ears and been swept under the rug," he said.

After a steady rise in homicides, North Charleston was ranked by one report in 2007 as one of the country's most dangerous cities, according to the Post and Courier newspaper.

In response, local officials expanded community policing, embedded officers in troubled neighborhoods and worked to build relationships with the residents on their beats, the paper reported.

Even though the city's crime rate has now ebbed, "you don't change cultures overnight," said Charleston County Sheriff Al Cannon.

"Citizens complained years ago that they did not have enough policing and that they only saw police when something bad happened," he said.

But many of the city's black residents see things differently. Police are known for stopping black residents with little cause, said Prince Williams, 62, who lives in the neighborhood where Scott was gunned down.

Williams recalled that Slager also stopped him once for a broken tail light, and he did not like how the officer treated him.

"He is a problem," Williams said. "He's been a problem."

Slager, who joined the department in 2009, had no prior record of discipline for improper use of force, according to his department file. Before his arrest, he said through an attorney that he feared for his life when he shot Scott.

Like much of the U.S. South, South Carolina has a checkered history when it comes to race relations. The state's endorsement of the Confederacy and slavery ran deep in the 1800s and, in more recent decades, white support for so-called "Jim Crow" segregation laws kept black residents marginalized.

The Confederate flag still flies on the grounds of the statehouse in Columbia.

In the past year, South Carolina activists have been encouraged somewhat by the indictments of several white officers accused of shooting unarmed black men, but such arrests are still rare and convictions even more so.

An analysis by The State newspaper in Columbia found that police in South Carolina fired their weapons at 209 suspects during a five-year period. Only a handful of those officers were accused of a crime and none were convicted, the paper found.

Asked on Wednesday whether a more diverse police force is needed, North Charleston Mayor Keith Summey told reporters there is a limited pool of minority applicants from which to hire.

Cedric Alexander, president of the National Organization of Black Law Enforcement Executives, said in an interview that police agencies need to try harder.

"Saying you can't find them isn't acceptable anymore," Alexander said.

Related: White US policeman sacked after shooting fleeing black man eight times before handcuffing body