A gunman who killed nine people during a shooting in Munich, Germany, had planned the attack for a year, the Bavaria state prosecutor's office has said.
A spokesman also said the victims of the shooting were not classmates of 18-year-old student David Ali Sonboly who has been identified as having carried out the attack.
The teenager is said to have been obsessed with mass shootings and is believed to have hacked a Facebook account in an attempt to lure people to a shopping mall where the attack took place.
The prosecutor's office also confirmed that a semi-automatic 9mm Glock handgun used in the attack was purchased on the internet illegally.
Authorities have not been able to interview the teenager's parents, the spokesman added.
Nine people were killed when a gunman opened fire at a shopping centre in Munich - seven of whom were reportedly teenagers.
A gunman who killed nine people and at a Munich shopping centre was German-born and had no links with Islamic State, authorities say.