German police believe that the lone, teenaged German-Iranian gunman who shot dead 10 people, including himself, in Munich was inspired by the massacre in Norway five years ago of 77 people by Anders Behring Breivik.
Munich police chief Hubertus Andrae said the gunman, a student who has so far not been named, acted alone when he opened fire in a McDonalds restaurant and a nearby shopping centre on Friday.
Andrae said he the assailant had no connection to the Islamic State extremist group, which has claimed recent attacks in Nice, Paris, in which 84 people died, and a knife-and-axe attack on a train in Germany in which five people were injured.
Instead, investigators found material on mass shootings in the gunman's room when they raided his family's Munich apartment early Saturday after Friday's night spooting spree in which 27 people were injured.
"Breivik would have played a role. It is obvious that it did," Andrae told a press conference, referring to the material in the gunman's room, which included a book entitled, Rampage in My Head - Why Students Kill.
The Munich attack coincided with events in Norway making the day five years ago when Breivik began his rampage by killing eight people after he detonated a homemade bomb in central Oslo.
This was before he launched a deadly shooting spree on the nearby island of Utoya where hundreds of teenagers were attending a Workers' Youth League camp.
In her first public comments since the shooting, Chancellor Angela Merkel said Saturday that Germans are mourning those who died and "share the pain" of the victims' families and friends.
The chancellor was speaking after a special meeting of the German security cabinet.
Police say they are still trying to verify a series of mobile phone videos of Friday's attack, which have been screened by German media and show the panic in the shopping centre when the attacker opened fire.
Another video apparently showed the person believed to be the gunman declaring in the video filmed by a nearby resident: "I was hospitalized for psychiatric problems.
"I am a German," the man is also heard saying. "I was born in Germany."
Police believe he may have also tried to lure his victims to the McDonald's where he launched his shooting spree with a fake Facebook post offering free meals.
Munich was slowly returning to normal on Saturday after authorities placed the Bavarian capital on high alert, temporarily shutting down the city's mass public transport services, evacuating the main railway station and calling on people to remain in their homes.
The shootings came less than a week after an axe-and-knife attack by a 17-year-old Afghan refugee on passengers on a regional train and a passer-by near the Bavarian town of Wuerzberg.
Munich state prosecutor Thomas Steinkraus-Koch said that his office is treating the Munich attack as a classic case of someone running amok, with the shooter having "no political motivation" and having not been influenced by the Wuerzberg attack.
Steinkraus-Koch also believes the attacker was suffering from psychiatric problems, saying investigators have so far not establish details of his mental state.
"We have indications that the offender could have been suffering from a significant mental disorder," Bavarian Interior Minister Joachim Herrmann told a press conference.
Andrae also believes that the shooter carried out the attacks alone and apart from several very minor incidents had not come to the attention of any authorities prior to Friday. He also ruled out the shootings having any link with refugees.
Police say that a gun used in the attack people was likely to have been obtained illegally and were trying to establish how he got it.
Five of those who were gunned down in Friday's attack were under the age of 18, police said.
Three Turkish citizens were among the dead, Foreign Minister Mevlut Cavusoglu was quoted as saying by Turkey's state-run Anadolu news agency.
Police said that the attacker, who was born and grew up in Germany, was carrying 300 rounds of ammunition in a rucksack.