The question is not whether they were legally responsible or whether they should have received the Islamically appropriate penalty - i.e. retaliation - if the next of kin had demanded it (and if you had read the article, you’d have known that some of the victims’ families do not support this policy). The point is that life without parole is (a) not the same as retaliation and (b) an unusually harsh penalty. Some would say it was much harsher than the death penalty, particularly for someone that young. No other jurisdiction, to my knowledge, imposes it (at all, let alone on young teenagers, and let alone without giving the judge any discretion) for anything but the worst of murderers (meaning the most serious terrorist and sex offenders).

Rather, it is you who make no sense. Anybody above the age of puberty is, in Shar’i terms, a legally responsible adult, subject to whatever punishment the Law metes out for his crimes.