Dorothy Holmes, the mother of Ronald Johnson, speaks at a news conference on Dec. 1, 2015, demanding the release of the dash-cam video of her son being shot in the back by Chicago police in October 2014.

Dorothy Holmes, the mother of Ronald Johnson, speaks at a news conference on Dec. 1, 2015, demanding the release of the dash-cam video of her son being shot in the back by Chicago police in October 2014.

*The State’s Attorney’s Office has shown a video of a white Chicago police officer fatally shooting a young black man, the second such video to be released within the past two weeks.

Cook County State’s Attorney Anita Alvarez announced Monday that she’s not charging Officer George Hernandez in the shooting death of Ronald Johnson III in October 2014, because a dash-cam video of the shooting shows Johnson wielding a gun.

Alvarez played the video and a sample of 911 recordings at a news conference at which she announced her decision not to charge Officer George Hernnadez with any offense, reports the Chicago Tribune.

Alvarez called Hernandez’s actions “reasonable and permisable,” citing that he was running toward a police vehicle and a public park on the South Side.

At the news conference, Assistant U.S. Attorney Lynn McCarthy said the office sent the video to an FBI laboratory to try to establish visual proof that he held a gun in his hand in the seconds before he was shot.

After Johnson fell to the ground, officers observed weapon in his hand, McCarthy said. The weapon was loaded with 12 live rounds and was connected to a shooting from 2013, prosecutors said.

Alvarez said the FBI decided not take part in the criminal investigation last year after its agents had viewed the video of Johnson being shot twice.

The video’s release Monday follows an effort by the family of 25-year-old Ronald Johnson III to force the city to make public the video that they say shows an officer shooting him in the back.

Nearly two weeks ago, the city released a video that shows the fatal shooting of 17-year-old Laquan McDonald, who was shot 16 times. Officer Jason Van Dyke has been charged with first-degree murder.

One major distinction between the two cases was allegations that Johnson was armed with a gun. Police, who described Johnson as a known gang member, said they recovered a gun at the scene, but Attorney Michael Oppenheimer, who represents Johnson’s mother, Dorothy Holmes, contended police planted the weapon after shooting an unarmed Johnson.

Watch the dashcam footage of Ronald Johnson’s shooting below: