It's the same situation as Mark Duggan over here. There's a lot of bitterness and angst left over from how black people were previously treated. Only difference is over here it became more of a class thing than a race thing when the scummy underclass jumped upon black anger as an excuse to loot. Over there they're still disenfranchised in some areas.
The black community still bringing up slavery is like me refusing to speak to my mates German wife. Its history, leave it there.
From the videos shown in the news the kid knew how to hold and point the gun and that's enough to scare anyone.