Rivera was shot and killed by a stray bullet earlier this week on the West Side. A 16-year-old male offender has been charged with multiple felonies for first-degree murder and for personally discharging a firearm that caused death.
The charges were announced in an afternoon press conference held by Chicago Police Department Superintendent Larry Snelling and other CPD officials.
CPD announces charges in fatal shooting of 7-year-old boy on West Side
Police said the 16-year-old suspect also had an active warrant prior to the fatal shooting for failing to appear in court on an unrelated robbery charge. An unrelated stolen weapon was also discovered in his home, but the assault-style rifle police say was used in the shooting has not yet been found. The offender will not be named by Chicago police because he is a juvenile.
Detectives said he was seen on surveillance video running away from the scene Tuesday after Rivera was shot in the chest. The suspect was found Thursday at his apartment and taken into custody.
Police recovered 13 rifle casings on scene but have not been able to find the weapon used in the shooting. They found a stolen weapon during the arrest that was not used in Tuesday's shooting.
Police said the 16-year-old boy is believed to be the only suspect in the shooting at this time. A motive for the shooting was not known, and police said he may not have been targeting anyone when he allegedly fired an assault-style rifle randomly and aimlessly.
"We cannot give you a motive for this offender's actions. I wish I could tell you more, but this is the frustration that we feel up here," said Chief Antionette Ursitti.
Police said they believe Rivera was about 300 feet away from the alleged shooter when he was struck by gunfire.
"It's absolutely maddening, heartbreaking that innocent children are dying in our city," Snelling said.
Earlier in the day Friday, there were demands for peace and justice on the West Side of Chicago.
The family of Jai'mani Amir Rivera was joined by neighbors and community leaders, marching to end gun violence after the 7-year-old boy was shot to death Tuesday outside his home.
CPD to announce charges in murder of boy killed in West Side shooting
"We are calling for city-wide peace," Saleshea Peterson with Hug a Child Make a Change said. 'We are calling for all the men to standup for a city-wide peace treaty and get a hold of these young guys."
Rivera had stepped outside to take something to his grandmother at the Oakley Square apartments near Jackson and Western when police said he was shot in the chest by a stray bullet fired in the area.
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On Thursday, his 10-year-old cousin, Joel, discussed the pain of losing Jai'mani.
"He had something to live for," Joel said. "He was only 7. He was just starting football, but he was taken away."
Thursday's march for peace comes as Chicago police say a person of interest is in custody for Rivera's murder.
Alderman Walter Burnett of the 27th Ward joined the family in the march, praying for justice in the case and peace across the city.
"Love is gonna out power hate," Burnett said. 'We need to continue to try to get guns out of kids hands and put something else in their hands, something positive."
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Meanwhile, children held up signs surrounded by their community, all of them calling on Mayor Brandon Johnson to find solutions for violence in Chicago.
"Mayor I have a question for you. Are you doing this for your reputation or for our future?" Joel said.