Looking into it, the people who lit the mattress on fire are dumb as forget.
They:
* Lit a fire because they were upset over what they admit to be basically nothing
* One of them admit they wanted to just "Leave" the refugee centre, but didn't elaborate
* There was an untranslated interview about how one of the suspects was complaining about food quality, he wasn't a refugee from Syria, this might be where the nutella thing came from
* After lighting the fire, they straight up confessed to doing it