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cnn |  Bynes said McCulloch's ties with police in the county could cloud his judgment.

McCulloch's father was a police officer and was killed on the job in 1964 by an African-American man, when McCulloch was 12, Magee confirmed to CNN. In addition to his father, McCulloch's brother, an uncle and a cousin all served with the St. Louis Police Department, and his mother worked as a clerk at the department, Magee said.

McCulloch, who as a teenager lost a leg to cancer, made it his career ambition to become a prosecutor. He was quoted by the St. Louis Post-Dispatch as telling a reporter, while first campaigning for the office: "I couldn't become a policeman, so being county prosecutor is the next best thing."

McCulloch has no plans to step aside and Magee said it doesn't have any impact on how he will handle the current case.

"Mr. McCulloch is going to continue to do his job as he was elected to do," Magee told CNN.

While the Justice Department is conducting its own civil rights investigation, Ferguson elected officials are concerned about the local investigation. McCulloch has overseen controversial cases before, some including police officers and black suspects.

The petition being circulated points to a 2000 incident in which two suspected drug dealers were killed by two police officers, McCulloch never brought charges against the officers, concluding they acted in self-defense. A subsequent federal investigation found that the men were unarmed and not moving in the direction of the officers, but because the officers felt endangered, the investigation found that the shootings were justified, the St. Louis Post-Dispatch reported.

"He doesn't have the fortitude to do the right thing when it comes to prosecuting police officers," Nasheed said on CNN's "Newsroom" on Tuesday.

Chris King, editorial director at the St. Louis American, an African-American publication, said McCulloch has already "manipulated" the Brown case by the way he is releasing information. The St. Louis County Police released a convenience store video from just minutes before Brown's death that showed a person who resembled Brown stealing a box of cigars.

"All of this information should have come out all at once in group. By leaking out in pieces, he is encouraging this kind of speculation," King said on CNN's "New Day."

Concerns about McCulloch arose again after Missouri Gov. Jay Nixon replaced the St. Louis County Police with the Missouri State Highway Patrol for security last week because he said the initial law enforcement response to the shooting was excessive. McCulloch told CNN affiliate KMOV that the governor had "no legal authority" to make such a move.