David Ali Sonboly, the teenager who killed nine people in Munich on July 22, had been planning his attack for a year, German authorities say.
The 18-year-old, who killed himself after the attack, had a Glock pistol that police believes he may have bought on the so-called dark net.
Meanwhile police in Munich have announced the arrest of a 16-year-old Aghan friend of David Ali Sonboly.
They say he is under investigation for not reporting Ali Sonboly’s plans.
“There is a suspicion that the 16-year-old is a possible tacit accomplice to the attack,” a statement on Munich police’s Facebook page says.
The statement goes on to say that the youth reported to police immediately after the shooting on July 22, and was interviewed as somebody with a connection to Ali Sonboly.
In the course of the interviews, they discovered discrepancies in his statements.
Police say they are now investigating the teenager on suspicion of failing to report a planned crime.
The investigations will have to show to what extent he was responsible for a Facebook post inviting people to meet at a cinema complex near the main railway station in Munich.
Ali Sonboly himself had put up a Facebook post before his attack, inviting people to come to the McDonald’s restaurant where the shooting began.
Seven of the dead in the shooting at the Olympia shopping centre were teenagers – two Turks, two Germans, a Hungarian, a Greek and a Kosovan.
A further 35 people were injured, but only four of them have bullet wounds – many were hit fleeing the scene.
According to the state government officials, the victims of the attack had not been specifically targeted and were not classmates of the gunman.
Also they did not include three youths allegedly involved in bullying Ali Sonboly when he was at school.
Head of Bavaria’s criminal police Robert Heimberger said Ali Sonboly had been planning the attack since he paid a visit last year to the town of Winnenden – the scene of a previous school shooting in 2009 – and took photographs.
Robert Heimberger said it was likely the Glock pistol – which had been reactivated – was bought on the “dark net” market, an area accessible only with the use of special software. It had been a theatre prop.
Ali Sonboly was said to be a keen player of “first-person shooter” video games.
Robert Heimberger added that the parents of the gunman remained in shock and were not able to be interviewed.
He also said police had not found the manifesto of Norwegian mass killer Anders Behring Breivik when they searched Ali Sonboly’s room at his parents’ flat.
A day earlier, officials had raised the possibility of a link to Anders Breivik, whose own attack was carried out five years earlier to the day.
As to Ali Sonboly’s state of mind, a spokesman for the Munich prosecutors’ office told a news conference that the gunman had spent two months as an inpatient at a mental care facility in 2015 and was afterwards treated as an outpatient.
“The suspect had fears of contact with others” and also depression, Thomas Steinkraus-Koch said.
However, there was no evidence of any political motivation.
Senior German politicians have called for tighter controls on the sale of guns in the wake of the shooting at the Olympia shopping centre.
Munich’s police chief has urged the media to respect the privacy of those affected by the attack on July 25, when schools reopen.
The 18 year-old attacker who killed nine people in Munich on July 22 was obsessed with mass shootings and had an obvious link to Norwegian mass murderer Anders Behring Breivik, German police say.
Police who searched the gunman’s room say they found written material on attacks.
The young man, who later killed himself, had a 9mm Glock pistol and 300 bullets.
Police are investigating whether he may have lured his victims through a Facebook invitation to a restaurant.
The man is suspected of using a fake account under a girl’s name to invite people to the McDonald’s restaurant where he launched his attack.
Anders Breivik murdered 77 people in Norway on July 22, 2011, killing eight with a bomb in the capital Oslo before shooting dead 69 at a summer camp for young centre-left political activists on the island of Utoya.
Now 37, Anders Breivik is held in solitary confinement in Norway after being sentenced to 21 years in 2012. He recently won an appeal against the tough regime of his incarceration.
Breivik harbored radical right-wing views and said his attack was aimed at stopping Muslim immigration to Europe.
Yesterday’s attack at Munich’s Olympia shopping mall also left 27 people injured, including children.
Seven of the dead were teenagers. Three victims were from Kosovo, three from Turkey and one from Greece.
According to police, the gunman had been in psychiatric care, receiving treatment for depression.
“We are in deep mourning… we share your grief,” said German Chancellor Angela Merkel after chairing a meeting of the national security council.
Flags are to be flown at half-mast across Germany in mourning
Munich police chief Hubertus Andrae said there was an “obvious” link between the new attack and yesterday’s fifth anniversary of Anders Breivik’s attacks in Norway, when he murdered 77 people.
A spokesman for the Munich prosecutor, Thomas Steinkraus-Koch, said the killer might have been receiving psychiatric care.
“We are assuming that he may have suffered from depression,” he said.
“As far as we know he has no criminal record. In 2012 and 2010 he was a victim of an attack – on one occasion he was beaten by three young offenders.”
Hubertus Andrae warned the number of injured could increase if people who had fled the scene came forward. Ten people were critically ill, including a 13-year-old boy, he said.
First reports of the shooting came in just before 18:00 local time on July 22.
Witnesses say the attacker opened fire on members of the public in Hanauer Street before moving on to the shopping mall.
A grainy video appears to show a man firing a gun outside McDonald’s as people flee.
Another video shows the gunman walking around alone on a flat roof before again opening fire. He can be heard shouting at the person filming, saying at one point: “I’m German.”
Police said the gunman was a dual German-Iranian national who was born in Munich. His name has not been released.
The attacker’s body was found about half a mile from the mall. He had no known links to ISIS, police said.
Police have ruled out any connection to ISIS.
Fears of a new ISIS attack had been high just four days after a teenage Afghan asylum seeker stabbed and injured five people on a train in Bavaria before being shot dead by police.
Claiming the attack, ISIS later released a video showing the 17-year-old brandishing a knife and making threats.