We also met social workers from Sweden's SiS, the youth homes where over-15 child offenders are sent. Staff are doing what they can with the resources they have to reform these boys, but say they are overwhelmed by the number of gang-involved children coming into their care

The picture isn't completely bleak - the government is introducing tougher sentences & other reforms to try and address the issue. We visited schools run by Fryshuset, where kids are given jobs so they don't seek easy cash from gangs. Teachers monitor them around the clock.

A useful way of looking at the issue was suggested to me by Evin Cetin, a lawyer who has deeply researched it: they are child soldiers. Like those used by Isis, they're brutalised & manipulated by gangs, thanks in part to social media - which grants unprecedented reach to kids

- there is a significant international element to these crimes. The gang's leaders are not even based in Sweden, having already fled the country

The most apparent driving factors are urban poverty, drug addiction and, in cases involving kids from a migration background, a deep sense that Swedish society just doesn't care about them. And -

We have also seen video footage of these crimes - some kids film the "job" for proof of payment - and text messages chats between kids and their gang "handlers" that paint a sinister picture, in which gangs are using children as proxies for drug turf wars.

The Telegraph interviewed Swedish police officers, prosecutors, lawyers, teachers, social workers and former gang members to build up a picture of why this is happening. That picture is very complex and there are quite contrasting views in Sweden over what's truly to blame.

Many - though not all - of the kids committing these crimes come from an impoverished, 1st/2nd generation migration background. As do the victims' families, whose prospects of justice are slim due to a culture of fear and omerta

The crimes are mostly committed by teenage boys, who do not necessarily have gang links - social media has revolutionized the gangs' ability to find willing volunteers. Girls & kids w/ mental disabilities are increasingly preferred by middle men who post the contracts online.

The number of children suspected of involvement in these killings in Sweden has exploded over the past year. Gangs, aware that under-15s cannot be prosecuted, are posting contracts on Snapchat and other platforms, targeting kids. They pay as much as £13,000 per hit