CHICAGO (CBS) — About 200 activists made 16 laps around City Hall on Friday, demanding a federal investigation of how Mayor Rahm Emanuel and Cook County State’s Attorney Anita Alvarez handled the Laquan McDonald case.

They circled the building once for each time McDonald was shot by Officer Jason Van Dyke last year on a Southwest Side street.

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Cook County Commissioner Richard Boykin said the protesters want the city to release all dashcam videos related to police shootings. They’re also demanding a thorough federal investigation of how the mayor, the Chicago Police Department, and Alvarez’s office handled the investigation of and response to the fatal police shooting.

“This cover-up began here at City Hall, and it began with the state’s attorney. Anything less than a full investigation of the mayor himself – and what he knew, and when did he know it, and what he did with that information – is unacceptable,” Boykin said.

Boykin also wants an independent prosecutor to handle the murder case against Van Dyke. He also called for the creation of an independent civilian police review board.

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Rev. Ira Acree said the public has lost trust in the mayor’s office.

“Why did you suppress the evidence for 13 months? Was the $5 million hush money? People are asking these questions, and we want to know now,” he said.

Alvarez’s office did not charge Van Dyke with murder for more than a year after he was killed, and only after a Cook County judge ordered the city to release dashcam video of the fatal shooting.

Months before that, Emanuel’s office convinced the City Council to approve a $5 million settlement with McDonald’s family – even before the family filed a lawsuit, and without showing aldermen the video – just weeks after Emanuel survived a runoff election.

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The protesters said they won’t stop marching until there is more change at City Hall.