Police said Friday that a person of interest was identified and after a search warrant of the person's home, a gun was located and seized.
The suspect remains in custody as police investigate.
Round Lake Beach police said they responded at about 9:10 p.m. to a residence in the 1500-block of Cherokee Drive and found the wounded girl.
The girl was transported to a hospital, where she died, police said. She has been identified to the Lake County Coroner as 15-year-old Valeria Rodriguez.
Investigators said someone outside of the home fired a gun and a stray bullet entered the home, hitting the girl. Her family told ABC7 she was eating dinner in the kitchen when she was shot.
Police said it did not appear that the girl was targeted in the shooting.
Kids were playing on a playground when a barrage of bullets was sprayed on the normally quiet block, neighbors told ABC7. Some said they no longer feel safe inside their own homes.
"He came out to take out the trash. There were kids playing outside," neighbor Jacqueline Santana said. "But moments after, we saw emergency vehicles. It couldn't have been shortly after, you know? Kids are playing and this happens... Especially having my family here on that day, yesterday, I can't imagine. It could've happened to any of us."
Weeks ago, the family was celebrating the victim's Quinceañera, to now mourning the teenager's sudden murder.
"They were out here dancing and trying to prepare for that," an anonymous neighbor said. "The kids heard a pop, but they just thought it was fireworks... I'm just confused on how and why it happened."
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"I just saw the mom crying," Santana said. "It was just very devastating. I almost wanted to cry myself."