The 18-year-old German-Iranian gunman who killed nine people in Munich on Friday began planning the attack one year ago after visiting the site of a 2009 school shooting in southwest Germany that killed 15 people, a Bavarian state official said on Sunday.

Robert Heimberger, president of the Bavarian state crime office, said material founded at his home showed the gunman was an avid player of violent video crimes who purchased his weapon -- a reactivated Glock 17 pistol -- on the so-called dark net, an area of the Internet accessible only via special software.

Heimberger said the parents of the gunman remained in shock and were not able to be interviewed. An official of the state prosecutor's office said the shooting victims did not include any classmates of the gunman.