"There is no indication that there is a link to ISIS," Andrae said.
That the shooting was carried out on the fifth anniversary of white supremacist Anders Breivik's deadly rampage in Norway indicated that the attack may have been motivated by far-right ideology, he said.
"The connection is apparent," Andrae added.
It also appeared that the attacker had hacked a young woman's Facebook account and posted a message to lure people to the mall for a free meal, said police investigator Robert Heimberger.
Munich woke up to a state of emergency the day after the shooting spree, with police scouring the city for clues to explain why the teen opened fire at a McDonald's attached to the Olympia Einkaufszentrum shopping center Friday night.
The 18-year-old German-Iranian gunman who apparently acted alone opened fire near a busy shopping mall in Munich on Friday evening, killing at least nine people in the third attack on civilians in Western Europe in eight days.
The pistol-wielding attacker, identified by Munich police chief Hubertus Andrae as a dual national from Munich, was later found dead of a suspected self-inflicted gunshot wound.
The shooter was believed to have staged the attack alone, opening fire in a fast food restaurant before moving to the mall.
In addition to determining the motive, police will have to find out how the 18-year-old got the firearm used in the attack in a country whose gun control system is described by the U.S. Congress Library as being "among the most stringent in Europe."
The gunman, whose body was found on a side street near the mall, was not identified but Andrae said he was not previously known to police.
Police commandos, armed with night vision equipment and dogs, raided an apartment in the Munich neighborhood of Maxvorstadt early on Saturday where the German newspaper Bild said the gunman lived with his parents.
"I am shocked, what happened to the boy? Only God knows what happened," Telfije Dalpi, a 40-year-old Macedonian neighbor of the family told Reuters. "I have no idea what happened - but he was a good human being. I have no idea if he did anything bad elsewhere."
There was a huge police presence in the street, which lies just north of Munich's old city.