I’m not gonna make a personal judgement on the question you asked, since as far as I have read, so far only 1 eyewitness has claimed that he said so. Also, based on Sonboly’s direct self-proclamation in the actual video he insists to be a German, born & raised. He doesn’t claim to be a muslim. That’s his self-perception.
But I understand the ideologically motivated point you are making - see my post #43. Though the recorded video conversation points to other elements at play, not necessarily ideologically (Islam) based. So, I’ll wait until the cops establish or at least suggest a motive for his actions.
As for your second point, yes, Andres Behring’s actions were ideologically motivated, he actually confessed the reason for his actions (not too dissimilar to Sonboly). I am familiar with Behring’s case, and he was also diagnosed to have Narcissistic Personality Disorder, although not psychotic when he committed the murders.
But, if I were to speculate about Sonboly’s choice of McDonalds and kids in particular, similar to target chosen by the Andres Behring, I’d suggest Sonboly had serious issues with his own treatment as he was growing up, as he said in the video. Issues which most likely went unresolved. Since he shot himself in the head and is now dead, unlike Andres, we will never know for sure.
Are you a Muslim?