Seven of his victims were teenagers, five of them under 16.
Advertisement
The youth was under investigation for possibly having failed to report the plans of the gunman, who later shot himself, a police statement said.
The Bavarian State Crime Office said he had bought the illegal pistol used in the attack on the internet.
His victims included eight young people and one middle aged person, as well as more than two dozen people who were injured.
He added that despite that the shooter had been studying potential locations for the attack he did not choose specific victims.
But previous year, Sonboly visited the town of Winnenden and took pictures, said Robert Heimberger, head of Bavaria’s police, according to The Associated Press.
Heimberger also said the shooter likely obtained his weapon, a 9mm pistol, illegally via the dark web.
A spokesman for the Munich prosecutor, Thomas Steinktaus-Koch, said Sonboly might have been receiving psychiatric care.
Robert Heimberger, president of the Bavarian state criminal agency, told the news conference police were investigating findings suggesting the Munich gunman invited people to a fast food restaurant at the mall via the Facebook account.
Hueseyin Bayri, who witnessed one boy’s death, said the shooter screamed a profanity about foreigners and said “I will kill you all” as he pulled the trigger.
According to German authorities, the teenager did extensive research on mass shootings before carrying out the attack.
Police have not named the attacker, but said he had dual German and Iranian nationalities and was born and raised in Munich.
Merkel told reporters in Berlin that the train attack on Monday night and Friday nights deadly rampage in Munich had involved “places where any of us could have been” and have left Germans wondering “where is safe?”.
Advertisement
In 2015, Sonboly had travelled 250km (155.3 miles) to the site of the school shooting in Winnenden to take photographs of the murder scene.
