I saw this yesterday evening, and have been thinking about it on and off all day, partly because I started fixing my own bikes when I was about the same age. A very sad story indeed, but I think there are way too many facts missing to be able to work anything out. It seems pretty obvious that the brakes failed, but from reading the article, the lad built the bike himself (unsupervised?) then took it to the LBS to get it checked over. Did the LBS know he'd built it himself? Were they asked to check the whole bike, knowing that he'd just built it himself? If he only asked them to check the rear brake, then maybe they didn't even look at the front, and if he'd not built it properly then it would have left the shop like that. If an LBS is asked to fix a rear brake, are they also to be expected to check the whole bike for other faults? some things are easy to spot, but a cable clamp that's not fully tight might not show itself until you pull really hard on the brakes a few times and the cable pulls through. On a steep hill, only having the back brake won't be enough to stop you, especially if it's not adjusted properly, so maybe the front failed, and the back didn't? It also appears he wasn't an experienced rider (as much as you can be expected to be at that age) - he was standing on the pedals, not trying to drag his feet on the ground, on a tyre, etc... His mother running a chain of bike shops doesn't have to mean she knows what she's doing - running a shop and fixing bikes are two completely different things, although many LBS owners can do both of them very well. And what is a kit bike? To mean, that means a kit of parts that you buy and assemble - not the same as buying each part separately and putting them together. A "kit" would have instructions, a guide to follow, safety information...
Just a tragic accident that might have been avoidable, but then most of them are.