[Livia]

Originally Posted by DemolitionRed

Actually, its not. Apparently, ISIS claim of responsibility contained no detailed information about the attack that wasn't already publicly known, so German authorities are currently working under the assumption that ISIS had no advance knowledge. In that case, their claim of responsibility would be based on nothing but speculation. Just as we are guessing.

Firstly, IS put out the call to Muslims worldwide, asking them to attack the infidel in any way they can, as a Soldier of IS. The more weak and criminal minded the person the more likely they will hear that call.

Secondly, when terrorist groups claim responsibility for atrocities - which many do, after every attack - the Security Services don't take their word on good faith. If they announce IS has taken responsibility you can take that to the bank. Whether or not your Google search acknowledges that.