Chicago Police announced on Twitter Sunday that they had arrested a 14-year-old boy in connection with the sexual assault of a 15-year-old girl that had been streamed live on Facebook in March.

The boy faces felony counts of aggravated criminal sexual assault, manufacturing of child pornography and dissemination of child pornography, police said. They said during a Sunday news conference that an arrest warrant had been issued for a second teenager and that they were actively searching for him.

The girl was reported missing from Chicago’s Lawndale neighborhood after she went to the store and did not return. Then the girl’s mother was alerted to the Facebook Live video of the attack, which she showed to Chicago Police Superintendent Eddie Johnson. The girl was found the next day, taken to the hospital and reunited with her family.

Police have said that the attack involved five or six people, and that 40 people watched the assault live on Facebook and did not call the authorities.

“You know, we’ve seen a couple of acts in this city now in the last few months involving social media. And it just disgusts me that people would look at those videos and not pick up the phone and dial 911,” Johnson said.

Police have since moved the girl and her family to a “safe space” after she was getting taunted and threatened. The girl’s mother said that her daughter had been receiving online threats after the attack and that kids in the neighborhood were ringing the doorbell looking for the girl, the Associated Press reports.