I live a few blocks from this incident. It happened on Tues night, the Thurs before that we had a bunch of kids arrive from the same general direction and a series of skirmishes took place with my neighbours. On the Fri night a bunch of kids on bikes accompanied by a car arrived and a neighbour was stabbed. Police attended both incidents.
This sort of thing is not very common here, it happens only sporadically. Its not necessarily symptomatic of deprivation or anything else, there are loads of kids around here living the same sort of existence and the majority of them get by without forays into crime, violence etc.
Some years ago I witnessed a bit of 'gang culture' arise on this patch. There was a very definite leader and when he left the scene the gang subsided straight away. Quite decent kids if you got to chat with any, away from the 'gang'.