Police possibly showing that internet stuff is not exactly their forte: they had to be told about the shooters'
fifteen year old online forum buddy in Freiburg by a third party.
NP: dpa refers to them as whistleblower, admittedly that would explain the timing difference.
Otherwise, it's a high profile/high priority case, and if a random(?) guy on the net can connect the dots faster than a supposedly trained professional, it wouldn't make them look terribly reliable.
TL;DR aka I'm too lazy to click on the link:
Fellow-minded fifteen year old Internet acquaintance of the Munich shooter
Posted self-incriminating stuff, chatted extensively with shooter, but no complicity in shooting
Had been preparing for months
Owned bullets/magazines, knifes/daggers, but no gun
Also chemicals and a plan to create explosives
Finally, a copy of the escape floor plan of his own school
Got busted by a guy on the net, raided by police, taken into custody and forwarded to a psych ward.
Is cooperative, admits to wanting to go on a rampage, but later deciding against it.
Will be charged with possession of weapons, but concrete plot to raid school may be harder to prove.
At least this guy will receive the help he needs before he drags others down with him. Gotta count your blessings, I guess.