Outraged citizens of Chicago say they are taking to the streets Monday night after the Cook County State's Attorney on Monday announced there will be no charges filed against the police officer who fatally shot Ronald Johnson III, a black man, last year—a decision that was prompted by what Johnson's family attorney described as "a whitewash, a cover-up."

During a lengthy press conference Monday afternoon, Cook County State's Attorney Anita Alvarez revealed dash-cam footage of the shooting, which Johnson's family had sought for over a year. The footage shows officer George Hernandez shooting at Johnson five times, striking him twice in the back as he fled.

That announcement came just hours after U.S. Attorney General Loretta Lynch said the Department of Justice had launched an investigation to determine if the Chicago Police Department was guilty of systemic violations of law, focusing on a pattern of deadly violence against the city's black community. The probe comes in response to growing anger over what groups say are the crimes of the CPD—from the legacy of disappearances and torture that occurred at Homan Square to the police killing of Laquan McDonald, and recent allegations of a cover-up.

Protesters are planning to convene at 6:30 PM local time at the intersection of 53rd Street and King Drive, where Johnson was killed, to demand justice, adding their voices to the growing call seeking systematic change, starting with the resignation of Chicago Mayor Rahm Emanuel.

Tweets about #justice4Ronnieman OR #resignrahm

Johnson's mother, Dorothy Holmes, told reporters Monday that she was "very upset" it took Alvarez 13 months to release the video of the shooting and that the allegation that Johnson was carrying a gun at the time was a "bald-faced lie." Holmes vowed that she won't stop "until I get what I want for him, and that's justice."

Family attorney Michael Oppenheimer challenged the state attorney's claims that Johnson carried a weapon, saying a gun was planted and that witnesses testified that police told them what to say. Oppenheimer also described the state attorney's press conference, which used blown-up visuals—that Alvarez herself described as "grainy, dark (and) blurry"—to prove their allegations, as a "27-minute infomercial."

The Guardian reports:

Assistant state’s attorney Lynn McCarthy showed an image enhanced by an FBI computer forensics laboratory, which she said showed that Johnson was carrying a gun in his right hand when he was shot by Hernandez. Police witnesses told investigators a gun was recovered from Johnson’s body after the shooting.

Responding to a reporter’s question, Alvarez did not state explicitly that the video showed that Johnson was armed.

"I’m looking at this, and it appears to be an object in there," she said.

The uproar over the Johnson shooting comes less than 24 hours after an estimated 400 hundred people marched through downtown Chicago chanting "Resign Rahm" over the police killing and alleged cover-up of Laquan McDonald. On Monday, activists rallied in the hallway outside the Mayor's office, forcing a late afternoon press conference addressing the police scandal inside.

Young black organizers chanting for #LaquanMcDonald ahead of @ChicagosMayor's presser. #Ronnieman #ResignRahm pic.twitter.com/EDYNWcvc2H

— Thanks, Bastards (@MinkuAzad) December 7, 2015