CHICAGO (CBS) — Lake County prosecutors announced an investigation has determined a Zion police officer was justified when he shot and killed 17-year-old Justus Howell last month.

Identifying the officer publicly for the first time, Lake County State’s Attorney Mike Nerheim said Officer Eric Hill fired at Howell “in fear for his life,” after Howell ignored repeated commands to drop a handgun he was holding in his right hand.

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Nerheim said Hill would not face criminal charges for the shooting. He said at least four independent witnesses saw Howell running away from Hill with a gun in his hand, and refusing Hill’s orders to stop and drop the weapon.

Zion police have said Hill shot Howell twice in the back on April 4, near 24th and Galilee, after he allegedly ran down a street with a gun he’d stolen from another man.

An autopsy determined Howell was shot twice in the back, and his death was ruled a homicide, but that ruling does not determine whether the officer’s actions were criminal, just that the death was the result of injuries caused by the intentional acts of another person.

Nerheim used maps and surveillance video to illustrate what happened when Howell was shot. He said, while it’s difficult to see on surveillance video, Howell turned slightly toward Hill when the officer shot him.

“Officer Hill provided Howell ample opportunity to drop the weapon, and only fired when he felt that his life, and the life of his fellow officer, was in danger,” he said.

Police said a handgun was recovered at the scene after Howell was shot, but Howell’s family has questioned whether he was armed.

Outside the county building in Waukegan, Howell’s family staged an angry protest of the prosecutor’s findings.

“We’re not satisfied with this decision,” said Howell’s uncle, Derell.

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“We don’t want people out here to be tearing nothing up, or burning buildings, or anything; we just want justice. You know, my nephew’s name was Justus,” he said.

Derell Howell said his nephew was cheated out of life, and the family is devastated.

Nerheim said the case file included 26 videos and hundreds of photographs. He provided new details of the day of the shooting.

He said investigators determined Howell was trying to buy a gun last month, and a third person introduced him to 18-year-old Tramond Peet, who met Howell on April 4 to sell him a handgun for $600.

According to Nerheim, as Howell and Peet were walking around the neighborhood, Howell asked Peet to see the handgun, and after Peet showed him a silver Kimber 9mm semiautomatic handgun, Howell took it without paying, and a struggle ensued.

Howell allegedly pointed the gun at Peet, and threatened to shoot him. Nerheim said Peet pushed the gun toward the ground, and it went off. He said at least five witnesses heard the shot, and one called 911.

Hill was among the officers who responded to the 911 call, and he saw Howell running away with a gun in his right hand. Nerheim said Hill chased Howell down an alley, and ordered him to drop the gun, but he refused, and when Howell began turning toward Hill, the officer shot him twice in the back.

Peet was arrested and charged with aggravated unlawful use of a weapon. Nerheim said Peet told investigators Howell threatened to shoot him after taking the gun.

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Howell’s death has sparked protests in the community, and some critics have compared it to the fatal shooting of Walter Scott in North Charleston, South Carolina. Former North Charleston Police Officer Michael Slager has been charged with first-degree murder, after investigators reviewed video showing Slager shooting Scott in the back as Scott was running away.