The St. Louis county prosecutor in charge of investigating the police shooting of an unarmed suburban teenager called on Missouri Gov. Jay Nixon to promptly decide whether he should remain on the case.

As a state grand jury prepared Wednesday to examine evidence regarding the Aug. 9 fatal shooting of 18-year-old Michael Brown by Ferguson police officer Darren Wilson, St. Louis County Prosecutor Bob McCulloch told reporters that Nixon's indecision on his status in the probe is "a distraction."

The shooting provoked more than a week of clashes in the St. Louis suburb of 21,000, drawing international attention as it became a symbol of heavy-handed police tactics and racial inequality in the U.S. As violence appeared to wane Tuesday, attention has turned to the investigation of the officer, who shot the unarmed Brown six times.

McCulloch, whose police-officer father was killed in a shooting more than 50 years ago, wouldn't conduct an impartial investigation and should recuse himself, black residents have said.

While the prosecutor has denied the allegations and said he has no intention of voluntarily stepping aside, Nixon, who has the authority to remove McCullough, has not stated whether he should remain on the case.

"All I'm asking of the governor is to make a decision — yes, you're on the case, no, you're not on the case," McCulloch said during a news conference in Clayton, Missouri. "He's dodging the question."

A call to the Democratic governor's office in Jefferson City, the state capital, was not immediately returned.

McCulloch said the shooting death of his father has "made me an advocate for victims of violence."