Chicago prosecutors announced on Monday that criminal charges will not be filed against the police officer who fatally shot Ronald Johnson in the back in October 2014.

According to Cook County State's Attorney Anita Alvarez, Johnson was armed with a loaded gun at the time of the shooting, and Officer George Hernandez was justified in opening fire as Johnson was fleeing the scene.

During a news conference, Assistant U.S. Attorney Lynn McCarthy presented a dashboard camera video of the shooting, which appeared to show the 25-year-old African-American man running away from police officers toward a public park around midnight. Several cops were chasing him when Officer Hernandez opened fire, shooting Johnson in the back of his shoulder and the back of his leg, reports The New York Times.

According to McCarthy, someone shot at a car that Johnson was riding in with three other people. He then left the scene and returned, but took off running while officers were interviewing one of the men in that car.

The grainy video, which lacked audio, gave no indication that Johnson was running with a gun in hand.

McCarthy showed a photo of a gun that she said was taken from the scene. She added that an independent police board, which reviewed the dashboard camera video, decided that the cop was not wrong to shoot Johnson.

Likewise, Alvarez called Hernandez's actions "reasonable and permissible" because she said Johnson posed a threat to police and potential bystanders as he ran into the park with a weapon, reports CNN.

However, Johnson's mother, Dorothy Holmes, and her legal rep continue to insist that Johnson was not armed.

Attorney Michael Oppenheimer described Alvarez and McCarthy's press conference as an "infomercial" full of information, which failed to conclusively demonstrate that Hernandez was justified in shooting Johnson.

"You can see no gun. There is no gun visible in Ronald Johnson's hand, because there was none," he said. "The Police Department planted that gun because there's no way anything would have stayed in Ronald Johnson's hand after he was shot."

Oppenheimer went on to say, "[The cop] had no right to shoot him in the back, no right at all."

The attorney also criticized police for removing the gun, said to belong to Johnson, from the crime scene in order to prevent bystanders from picking it up.

"No police officer will ever tell you that it's proper, or wise, or within the rules to reach down and to recover gun from a suspect's hand as he's lying on ground. They claimed that he was still breathing. He was dead. Do they really expect that he will come back to life and shoot him?" Oppenheimer said, according to CBS Chicago.

He also accused police of planting a gun in the grass to make it look like Johnson had it when he died.

"How in the world did all that grass get in that gun? He was holding it, according to them. He was running full speed, then the gun ends up gently laying on the top of his right hand. I would think that if you would drag up grass, you would almost have to drag it through the grass to pick it up. I think the officers, or detectives, or whoever did this added that for effect to show that there's some grass connected with the gun where the gun was found," he said.