> Was he yelling Allahu Akbar or some other mentally ill shouting cry? <
The perp seems to be a guy dressed as a girl. So my initial guess is that one of his victims used the wrong pronoun, or maybe teased him. And that set him off.
(See my post #34.)
By the way, I’m quite certain you’ve got the “mentally ill” part right, at least.
Sorry. I meant see my post #32.