Matt Slocum, Associated Press
Baltimore State Attorney Marilyn Mosby smiles as she is introduced before delivering the keynote address during the Women in NAACP Empowerment Forum and Brunch, Sunday, July 12, 2015, in Philadelphia. NAACP leaders are joining the call for a federal investigation of the North Charleston Police Department, echoing what local activists have been seeking since the shooting death of an unarmed black man by a white officer more than three months ago.

CHARLESTON, S.C. — NAACP leaders are joining the call for a federal investigation of the North Charleston Police Department, echoing what local activists have been seeking since the shooting death of an unarmed black man by a white officer more than three months ago.

Sherrilyn Ifill, the president of the NAACP Legal Defense and Educational Fund wrote U.S. Attorney General Loretta Lynch on Monday seeking a federal investigation of both the department and into the April shooting of Walter Scott.

Former North Charleston officer Michael Slager was indicted last month on a murder charge and faces 30 years to life in prison if convicted in Scott's death.

Slager fired as Scott tried to run away from a traffic stop in North Charleston on April 4. A bystander recorded the shooting on a dramatic cellphone video, fueling the debate about how white officers treat black people across the nation.

The Justice Department already is investigating whether there were civil rights abuses in Scott's death. But Ifill's letter seeks a wider investigation into what it calls racially-biased policing in the city.

The letter to the attorney general was also signed by more than 30 others, including six South Carolina state lawmakers.

Spencer Pryor, a spokesman for the city police department, said in a statement that the city "strongly disagrees with the characterization of the police department" in the letter and "feels a Justice Department inquiry is not warranted."

The letter said "the fatal shooting of Mr. Scott exposed to this nation another example of racially-biased policing and excessive use of force that has long existed in North Charleston."

It listed eight examples of what it said were excessive use of force by North Charleston officers during the past decade. Six of those incidents involved blacks.

The letter noted the Confederate battle flag was removed from the grounds of the South Carolina Statehouse in Columbia last week.

"While this is a welcome act, merely removing a flag long recognized as a symbol of racial hatred and intolerance will not eliminate racially-based policies and practices that have permeated policing in North Charleston," Ifill wrote.

The flag was removed following the killings of nine black church members during a Bible study in Charleston last month. Police have arrested a white man who had posed with Confederate flags and have called it a hate crime.

In the days following Scott's shooting, local civil rights leaders called for a federal investigation into all shootings involving law officers in Charleston County going back more than two decades.

They said at the time they don't have faith in the local police, prosecutor or the State Law Enforcement Division to conduct such an investigation and want a federal review of such cases dating back to 1994.