There are certain...kinds...of people who given an opportunity will steal almost anything just because it's there for the taking, even when they have no need for it at all (which might be if not an excuse at least a reasonable explanation).
I had no idea about the hair extensions thing in Ferguson, Mo. but given designer trainers, tvs, etc, etc were the kind of things that principally where stolen during riots in London a few years ago, I think we can be supremely unsurprised at this latest news.
Water is a) easy to come by in London no matter one's economic status, and b) extremely safe to drink. I know because I live there. There's absolutely no need whatsoever to steal bottled water.
Tempted to say 'not all blacks' because I do know (I'm sure many of us do!) a number of very morally upstanding, indeed faithfully 'Catholic' (if norvus ordo) black families. But I think that also muddies the waters of the larger issue which the posters above me have already identified...