I come from that area, Sydenham, and Forest Hill was within walking distance, through the park.
Chilling indeed (it was on the television news), but the perpetrator appears to have been deranged, possibly psychotic, running around screaming about Muslims and stabbing. We'll find out in due course but if that is the case, black and Muslim won't be relevant.
Did I dream it but wasn't there another violent incident in Forest Hill reported in the media a few months ago?