I think the 'pick and answer' idea is way too simplistic for such a complex problem, and in margins all of the above are correct. For sure lack of strong, male role models do leave teenagers somewhat compassless, and gangs take up that position who are in turn motivated by drugs and in turn by the money those drugs provide. Austerity has helped no-one, unemployment amongst the black community is far higher, along with single parents, and struggling mothers trying to keep things together find themselves overwhelmed and powerless to escape areas where knife crime and gangs are prevalent. This is not per se because they are black however, this is because of blatant inequality, magnified by poor economic trends, social isolation, poorer educational results etc etc etc.
It's very easy to say ' this is a black problem' it's not, it's a social problem which affects black teenagers far more than white ones for a whole host of reasons. Cure the race related social ills and you will cure the prevalence of young black people dying, but that is not an easy or quick process, and will take a generation or more to mend, but we can't simply dismiss this as a 'black problem', it's simply not, it's a problem with our society as a whole which has led to it appearing to be.