Police say they expect other juveniles and an adult to be charged.
Chicago Police Superintendent Eddie Johnson plans to give a press conference Sunday afternoon to give the public more details.
She then disappeared and was found two days later after the alleged assault was filmed.
A 14-year-old boy has been arrested in Chicago in connection with the alleged sexual assault of a 15-year-old girl that was streamed on Facebook Live.
"There's a second juvenile warrant that is out there", Commander of Area Central Detectives Brendan Deenihan said during Sunday's press conference. Guglielmi said the boy would be later brought to a juvenile detention center where a 14-year-old boy who was arrested in the case over the weekend is being held.
The teen boy is facing aggravated criminal assault and disseminating child pornography charges. Investigators have said the attack involved five or six males.
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Police Spokesman Jose Estrada says the video shows mostly closeops of the body parts which has made it more hard for police to identify anyone.
The victim's family told police that as many as 40 people watched the live stream without calling 911.
Deenihan said charges could not be filed against individuals who have taunted the family because no specific threats were made against the girl or her family. "They've humiliated themselves, humiliated their families, and now they're going to be accountable for what they did", Eddie added.
Johnson was initially approached on March 21 by the girl's mother, who was "desperately seeking help".
"This caused even more trauma for the victim", Deenihan said. Police are also working to keep her safe. He said the girl knew one of the offender and was lured into a residence located in Chicago's west side.
In January, an attack by four people on a 19-year-old man with special needs was partially broadcast on the social media site. "It makes you wonder: Where are we going as a society?"
The girl's relative Reginald King said a teenager alerted him to the assault on Facebook Live.