The gunman who went on a shooting rampage in Munich killing nine people had spent more than a year preparing his attack.
Bavarian investigator Robert Heimberger said the 18-year-old German-Iranian named in reports as Ali Sonboly visited the site of a previous school shooting in the German town of Winnenden and took photographs.
He said the attacker, who likely got his illegal weapon through the internet's "dark net" market, was an avid player of first-person shooter video games, including Counter-Strike: Source.
Thomas Steinkraus-Koch, spokesman for Munich prosecutor's office said there is still no evidence of any political motivation for the crime, nor that the shooter killed specific victims when he opened fire at a shopping centre and a McDonald's on Friday.
It was also revealed that the gunman had received two months' inpatient psychiatric treatment last year. "The suspect had fears of contact with others" and also depression.
The gunman took his own life following the attack in which 27 people were injured - 10 of whom are in a critical condition, including a 13-year-old boy.