Exactly how many young people are part of the networks is unclear, but according to criminologist Sven Granath, it is about hundreds of young people in the Stockholm area alone.

- Partly, through the digital revolution, you have gained access to weapons to a different extent, and older and younger people can also come into contact with each other more easily, he says.

In the video: Hear the criminologist tell how many children and young people there may be in Stockholm.