Police in Chicago are searching for five or six suspects, each of them men or boys, who they believe raped a 15-year-old girl who had been missing and broadcast it on Facebook Live.

Chicago police spokesman Anthony Guglielmi said the girl went missing on Sunday, the Associated Press reports, but police Superintendent Eddie Johnson was leaving a station in the Lawndale neighborhood on Chicago’s West Side late Monday afternoon the girl’s mother approached him with graphic photographs of her daughter being sexually assaulted on Facebook.

Johnson immediately ordered an investigation of the assault and contacted Facebook to remove the video. Guglielmi said as many as 40 people saw the video, but none of them reported it to police. The girl’s mother told Chicago’s WGN-TV that the girl’s uncle told her she was on Facebook Live and that’s when she notified Johnson.

“What’s even more disturbing, more than the fact that they did this, there were so many people that saw this and they didn’t pick up the phone and dial 911,” Johnson told WGN. “That’s just not right and (we’re) working on it and try to bring it to a successful resolution.”

Guglielmi sent out a tweet early Tuesday saying the girl had been sexually assaulted on Facebook, but minutes later she was seen walking about four blocks away from her home. Police returned her to her mother and both were being interviewed by authorities. Police are now attempting to find the owner of the Facebook page, according to WGN.

This incident is the latest crime streamed on Facebook Live in Chicago. Earlier this year four people were charged with hate crimes and kidnapping in the beating of a mentally disabled man while streaming the violence. Also, last summer, a 28-year-old man was shot and killed while recording himself on Facebook Live.

Attempts to reach Facebook by EBONY for comment were not immediately returned.