The Bavarian state crime office says David Sonboly bought his weapon on the so-called dark net, an area of the Internet accessible only via special software.
Robert Heimberger, president of the Bavarian state crime office, says Mr Sonboly had visited the site of a 2009 school shooting in southwest Germany that killed 15 people.
(translation) "The first inspection of his electronic data processing lead us to the conclusion that he began to plan his own attack after he took an interest in the Winnenden attack and visited there last year."
Meanwhile.. German Vice-Chancellor Sigmar Gabriel confirmed there was no connection to Islamic militancy ..after police conducted a search of the attacker's room.
Mr Gabriel says the revelation lowers the risk of follow-up attacks in Germany.
(translation) "All security forces in Germany are tense these days. We are worried all over Europe, but thank God, what we saw now doesn't lead us to expect follow-up attacks."
