While in St. Louis on Friday, the Rev. Al Sharpton renewed his call for a federal prosecution of the white police officer who killed the black teenager, Michael Brown.

A St. Louis County grand jury is investigating whether to implicate the Ferguson the police officer Darren Wilson in Michael Brown's killing. The panel is expected to complete its review by mid-November. Sharpton said leaks about the secret grand deliberations are undermining the investigation.

"The grand jury is tainted. The confidence of the family has been shattered," Sharpton told reporters after meeting briefly with Brown's parents and local activists at a breakfast rally before returning to New York. "We should turn this over to the federal government."

A tweet about an alleged conversation with a juror was investigated as a leak by the St. Louis prosecuting attorney. He said the Twitter account had been hacked, but there had been no leak from the jury.

The U.S. Justice Department is already undertaking its own investigation into whether Brown's civil rights were violate and a broader investigation into the policies and practices of the Ferguson police department. The Justice Department will need to prove that officer Wilson deprived Brown of his civil rights, according to The Associated Press. A process that is easier to prove when a person is handcuffed or beaten but difficult when police officers have latitude in their use of force.

On Aug. 9, Michael Brown, 18, was unarmed when office Wilson encountered him walking in the street with a friend. A scuffle started while Wilson was still in his police SUV and spilled into the street. Brown was shot six times and was killed. There are conflicting witness reports as to whether and when Brown had his hands raised, and whether he was moving toward Wilson when the final shots were fired. The shooting sparked protests and demonstrations due in part that people understood that Brown was surrendering as well as longstanding tensions between the majority-black residents and the majority-white city government and police.