A 13-year-old boy was fatally shot in his Northwest Side apartment Wednesday night and Chicago police arrested a 17-year-old boy in connection with the shooting, authorities said.

       The 13-year-old had been inside an apartment in the 5200 block of West Byron Street in Portage Park around 8:40 p.m. when for an unknown reason someone shot him in the chest, according to Chicago police.

       He was taken to Stroger Hospital where he was pronounced dead at 9:29 p.m.

       He was identified as Isaac Jordan, of the same block where he was shot, according to information from the Cook County medical examiner’s office.

       Chicago police said they recovered a weapon and arrested a 17-year-old in connection with the shooting. As of Thursday morning, he had been charged with aggravated unlawful use of a weapon with no FOID card. A police spokeswoman said no additional information was available.

       A source said the shooting appeared to be domestic-related, suggesting the 13-year-old and the 17-year-old arrested had a relationship. Police would not immediately comment on the nature of the relationship.

       It wasn’t immediately clear whether there was anyone else in the apartment at the time of the shooting.

       The teenager’s fatal shooting happened a little more than 24 hours after a 4-year-old girl was wounded during an unrelated shooting in the 600 block of West 61st Street Tuesday afternoon.

       The toddler had been sitting outside a home in Englewood when someone fired shots, striking her in the arm. Someone drove her to St. Bernard Hospital and she was transferred to Stroger Hospital. She had been listed in good condition, officials said. No arrests had been made in that shooting.

       Check back for updates.

       kdouglas@chicagotribune.com

       Twitter @312BreakingNews

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