It appears that this person was obsessed with genocide, in particular the genocide that took place in his parents home country, Rwanda. My own grandmother regularly spoke of how WW1 affected her family with two of her brothers killed, and so I think it likely that the genocide in Rwanda would have been mentioned as this boy grew up, and any family left in Rwanda would have been spoken of. Assuming that this is the case, and it would be in most families, how might this have affected him. Apparently he also showed obsessive interest in Somalian massacres and groups such as Al Qaeda.
It’s all speculation off course, with some correct information thrown into the mix, because we find his behaviour inexplicable, especially I suppose from the child of asylum seekers, who would be relieved and happy to be living here. The parents appear to have assimilated successfully, as has the brother, so what went wrong with him?