CHICAGO (CBS) — Chicago police said an 18-year-old man shot and killed an officer’s son last summer while the victim was sitting on his parent’s front porch with friends, because the gunman falsely believed the victims were rival gang members.

Anthony Moore has been charged with first-degree murder and attempted murder in the August 2016 shooting which left 19-year-old Arshell “Trey” Dennis III dead, and a friend seriously wounded.

Dennis, 19, was the son of Chicago Police Sgt. Arshell “Chico” Dennis.

trey dennis Police: Man Who Killed Officers Son Believed Victim Was In Rival Gang

A 19-year-old killed early Sunday morning is the son of Chicago police officer Arshell “Chico” Dennis, police officials said. | Dennis Family

Police Supt. Eddie Johnson, who once served as a patrolman with Sgt. Dennis, said it’s every officer’s greatest fear to have their own family fall victim to violent crime.

“Every police officer will tell you their greatest fear, beyond what could occur to them by doing their job, is when violence that they work so hard to prevent hits home,” Johnson said as he announced the charges against Moore on Friday.

anthony moore Police: Man Who Killed Officers Son Believed Victim Was In Rival Gang

Anthony Moore is charged with the murder of Arshell “Trey” Dennis III. (Source: Chicago Police)

Johnson choked up as he discussed the slaying of the younger Dennis.

“I know that there is nothing we could ever do to make up for what happened, but I hope this will help bring some sort of peace and closure to the family,” he said. “Every officer in this department took his murder personally, and we vowed not to stop until we found his killer.”

The younger Dennis was a junior studying journalism at St. John’s University in New York, and had come home to surprise his mother for her birthday last August.

Shortly after midnight on Aug. 14, 2016, he and two friends were sitting on his parents’ front porch in the Wrightwood neighborhood, when a group of gunmen walked up and opened fire on them, police said.

Area Central Detectives Commander Brendan Deenihan said Moore shot Dennis, mistakenly thinking he and his friends were rival gang members.

“These offenders did this because they believed Arshell and his friends were in an opposing gang, which is not accurate at all. Arshell was a college student, his friends were not in any gangs, his friends were not affiliated with any gangs, but these offenders … basically saw three male blacks in their late teens or early 20s sitting on a porch, and they decided that this was the opposing gang, and they decided to shoot these individuals.”

The younger Dennis was shot in the chest, and died at Little Company of Mary Hospital in Evergreen Park. A friend who was with him was seriously wounded, bur survived. His other friend was not hurt.

Deenihan said Moore later bragged about the shooting, believing he had killed a rival gang member. In addition to witness statements, detectives were able to collect surveillance video of two stolen cars the shooters used to drive to and from the scene of the shooting, Deenihan said.

Police said Moore has a juvenile criminal record, and was arrested six times within three months of turning 18 in November 2016. Deenihan said Moore already was in custody for another crime at the time he was charged with the shooting. Cook County Sheriff’s office records show Moore was being held at the county jail for possession of a stolen vehicle.

Moore was due to appear in bond court Saturday afternoon.

A $13,000 reward had been offered for information leading to an arrest in the case.

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