The 18-year-old suspect who opened fire at a crowded Munich shopping centre and fast-food restaurant, shooting nine people dead and wounding 16 others before killing himself, was obsessed with mass shootings, police said.
Investigators searched the unnamed suspect's home overnight and found a considerable amount of literature about mass killings, including a book titled "Rampage in Head: Why Students Kill". They believe he acted alone.
The gunman, dressed in black, went on a shooting spree at a shopping mall on Friday evening before committing suicide.
Among the nine killed were three Kosovans, according to the foreign ministry in Pristina, while Munich police said the injured included children.
The attack was carried out exactly five years to the day since mass killer Anders Breivik began slaughtering dozens of people in Norway.
'Breivik played a role'
Munich police chief Hubertus Andrae said: "Breivik would have played a role. It's obvious that he did."
He described the attack as a "classic act by a deranged person" and described an individual "obsessed" with mass shootings.
However, Germany's Interior Minister, Thomas De Maiziere, said it was too early to draw the link with Breivik.
De Maiziere added that there was "no indication of any connection to international terrorism". Police have not found any evidence that the attacker was linked to groups like the Islamic State of Iraq and the Levant (ISIL).
Munich prosecutor Thomas Steinkraus-Koch said the 18-year-old suspect, a German-Iranian whose name has been withheld for the time being - had suffered depression and reportedly undergone psychiatric treatment.
"There has been a suggestion that this individual, the perpetrator, had tried to lure people to that fast-food restaurant with the promise that he will buy food for them," said Al Jazeera's Dominic Kane, reporting from Berlin.
"He clearly wanted them to go to where he could shoot at them."
The attack sent Germany's third largest city into lockdown as police launched a massive operation to track down what had initially been thought to be up to three assailants.
'A night of horror'
Chancellor Angela Merkel said on Saturday that Munich had suffered "a night of horror.
"A night like this is difficult for us all to bear," she said. Speaking from her office in Berlin, the German leader added: "All of us, and I say this on behalf of the whole government, are mourning with heavy hearts those who will never be able to return to their families."
Armed with a handgun, the attacker opened fire at a McDonald's restaurant and continued along the street before entering the mall.
A police patrol shot and wounded the gunman but he managed to escape before police found the body of what they believed was the "only shooter".
A video appeared to show the gunman on a car park roof exchanging a tirade of insults with a man on a nearby balcony.
"I'm German, I was born here," the assailant replies after the man fired off a volley of swear words, including an offensive term for foreigners.
Police initially believed there could be up to three assailants.
But Andrae later said two others had "absolutely nothing to do" with the attack, and that they were simply fleeing the scene.
President Joachim Gauck said he was horrified by the "murderous attack", while US President Barack Obama voiced support.
"Our thoughts are with the victims, their families, and all German people. Europe stands united," EU foreign policy chief Federica Mogherini said on Twitter.
Source: Al Jazeera and agencies