They would have based their stories on what information was provided by the police.
Initial impressions can often prove wrong as you will be aware (the Rachel heroin death followup story after further investigation is an example) - all the papers carried pretty much the same facts, but some went OTT on the aspect of playing "violent" games and videos.
Someone has to direct the responsibility towards parents/guardians who should be seeing that their children do not have access to inappropriate material, I know it's not an easy thing to do, but, they are their children. It is all too easy to let someone else take responsibility, I sometimes think it is actively encouraged. As far as journalists are concerned I believe they publish first and If you are lucky, retract afterwards.
"There are always one or two who let the side down in any walk or area of life, so don't brand ALL journalists in such a fashion". One or two, is that dozens or hundreds?