A German-Iranian teenager acquired the semi-automatic pistol he used to kill nine people in Munich on the dark web and did extensive research on mass shootings, Bavaria's interior minister Joachim Herrmann (CSU) tells the B24 broadcaster.
The 9mm Glock handgun was smuggled into Germany and sold illegally to 18-year-old killer Ali Sonboly. The serial number on the weapon had been erased but police sources have revealed the firearm carried a certification mark from Slovakia.
It is believed the weapon used to kill nine people on Friday was a replica that had been converted to fire live ammunition.
Police seized his computer from the home he shared with his parents and younger brother.
By examining his hard disk they will be able to find out where the gun was purchased from and most likely who was involved in its handling on its route from Slovakia to Germany.
The 18-year-old had a copy of the manifesto of Norway attacker Anders Breivik saved on his computer and travelled "within the past two years" to the scene of a 2009 school shooting in the southern German town of Winnenden, Joachim Herrmann tells the broadcaster.