Police in Chicago have arrested a 14-year-old boy over the the sexual assault of a teenage girl by a group of young men that was broadcast live on the internet.
The attack on a 15-year-old victim was streamed on Facebook and watched by about 40 people who did not report it .
A Chicago police spokesman said more arrests were expected
The assault involved five or six people and the boy arrested "was one of the offenders in the video," police said.
He faces charges of aggravated criminal sexual assault, manufacturing of child pornography, and dissemination of child pornography.
The police spokesman has said officers were not aware of the attack, which happened about two weeks ago, until the girl's mother approached Police Superintendent Eddie Johnson as he was leaving a police station and showed him the video.
Johnson was "visibly upset" after he watched, both by the video's content and the fact that there were "40 or so live viewers and no one thought to call authorities," the police spokesman said.
The girl's family have been moved by police after she received online threats following the attack, and teenagers in her neighborhood were ringing her doorbell looking for her, the Chicago Sun-Times reported.
It was the latest incident in which Chicago police have investigated an apparent attack broadcast live on Facebook.
In January, four people were arrested after video showed them allegedly taunting and beating a mentally disabled man. The four accused in the attack have pleaded not guilty.
The shooting death in February on the city's West Side of a two-year-old boy was captured on Facebook Live by his aunt, who was also shot.