Organizers said Sunday that more than 20,000 people had signed online petitions seeking a special prosecutor to investigate the death of Michael Brown.

St. Louis County Prosecuting Attorney Robert McCulloch is in charge of the investigation. The petition asks him to step aside.

“Many community members don’t believe he can be fair and impartial,” state Sen. Jamilah Nasheed, D-St. Louis, said. She launched the petition drive with the goal of gathering 50,000 signatures. “We will continue to put pressure on him to resign,” she said.

Nasheed cited McCulloch’s investigation into the actions of two undercover drug detectives who killed a suspect and his passenger in a car on the parking lot of the Jack in the Box restaurant in Berkeley in 2000.

Grand jury proceedings are secret. McCulloch, in telling the public what the grand jury had found, repeatedly insisted that “every witness” had testified that the two detectives fired to defend themselves after the suspect tried to run them over with his car.

The Post-Dispatch reviewed the previously secret grand jury tapes and found that McCulloch’s public statements were untrue.