Dozens of people watched as 15-year-old girl in Chicago was gang-raped on Facebook Live, yet no one called the police.

The video, which has since been removed, is the second story to make headlines out of Chicago about a crime taking place on the social media live streaming service. In January, police charged four people for hate crimes after they allegedly tied up, beat and tortured a special needs student while a Facebook Live audience watched.

As Live grows in popularity along with the potential for harmful uses of the tool, police say it is important for users to know what to do if you see a crime or other dangerous activity on Facebook Live.

We spoke with the Chicago Police Department, which offered some tips for what to do if you see something bad happening on social media.