just to remind you alll that dos != ddos. the extra d stands for "distributed", meaning there is no single source for the attack, rather zillions of them (most likely a botnet) flooding the target. so i dunno what this kid did, but it definitely wasn't a ddos.
if this kid managed to take the servers down from home that would be evidence of a blatant security hole, either in software or in network setup. let's hope it was fixed.
also, as some pointed out, it is entirely possible that the kid's computer and account were compromised and the attack performed by someone else. but then again it most likely would have been another kid causing trouble, a serious attacker wouldn't expose a compromised machine so openly either.
and, i find the official explanation a bit cheesy, some more detail would be appreciated.