What does it have to do with paranoia? When a 12yo tries to kill god knows how many with a bomb on a christmas market then of course his motivation, radicalization and origin/influences are relevant.
Precisely. I'd group the "origin/influences" as "identifiers". In socialization process we adopt norms, customs, values and ideologies of our environment and of groups we associate with. We also tend to identify ourselves through the social institutions. These identifiers are important in a way that they form an idealized picture of what it means to be within this group. For example when I was young I identified myself as a bit of a nerd, therefore I strived towards doing nerdy things to be accepted with the nerdy social circles. Most of us don't identify as only one thing and that's good - the more labels you identify with, the more people it includes and the easier it is for you to relate to them.
You feel more connected and more empathetic to the people in the same group as you. That is why you see christian news outlets spreading news about the lives of other christians around the world, that's why national news tell you how many of your countrymen are affected by disasters happening abroad. We relate through association in the same group.
The identifiers are also a bit fluid. When someone does something rotten and they're associated with the same group, we tend to oust them. In terms of radicalization when Breivik committed his mass murder christians cried "he's not a true christian" and the far right cried "lone wolf", nothing to do with us! The same is applicable to for example the Paris terror attacks, we heard how the perpetrators were not real muslims over and over again. We also see the same in discussions about socialism etc. But the discussions of what is real christianity, islam or socialism are basically fruitless as the labels we associate with are our idealizations based on ourselves - I am a social democrat, therefore all other social democrats think like me (why else would they call themselves social democrats?)
Last of all the group identifiers can be used in exclusive manner. Usually there are certain attributes and stereotypes connected to those labels you're not. Therefore nationalists are racists who just want to kick everyone out and spit on them for good measure, and leftists just want to open the immigration floodgates with no regards to other citizens. The exclusivity can also be used to dehumanize others by labeling them under larger umbrella, I suspect the demonized group in this case was "Germans".
Your origin, if by that you mean the ethnic, cultural and/or religious etc. background is one of the most easily exploitable of these identifiers as you're basically born with them. Initially if you identify with a group, you tend to group us with others like you. Like in international conference with strangers, people tend to initially form in national groups - you have something in common. The problem really starts if the background is strict and exclusive as in the environment you're in only approves one small set of ideals and identifiers and keeps you out from the others (mind you, this can be achieved through your peers as well as your parents or both). That way you can easily be isolated from the society and be steered to seek social inclusion from very narrow sect of people, in this case ISIS.
Exactly. I just wanted to reiterate that its not a 'boys will be boys' kind of thing or something you can just erase from their heads shortterm.
Yes. In case of adolescents with violent and/or drug abuse backgrounds for example, they are usually taken to a long term custody away from the old social circles with social and psychological help provided to them. I'd presume this would be more or less applicable here. It could also be presumed that the same influences that were present in order to get him to this point, would probably still be present there. If a child becomes so antisocial at home as to plot a bombing, it's very likely his home isn't the best environment for him to be.
