Kim Hjelmgaard, and Doug Stanglin

USA TODAY

MUNICH — Germany's interior minister said Saturday that investigators turned up no link between Friday's deadly shooting rampage in Munich and international terrorism, but did find that the 18-year-old German-Iranian gunman was fascinated with mass killings, particularly an attack in Norway five years ago.

Interior Minister Thomas de Maiziere, Germany's top security official, identified the gunman in the attack that left nine people dead only as David, while the German media gave his name as Ali David Sonboly. The gunman died of a self-inflicted gunshot.

“There was material found in the apartment of the suspect that showed a particular interest in shooting sprees, (but) there is so far no indication of any connection to international terrorism,” de Maiziere said.

De Maiziere said David researched a 2009 school shooting in Germany, as well as the murderous attack by anti-immigrant agitator Anders Behring Breivik, who killed 77 people in Norway on July 22, 2011.

Initial investigations also suggested that the shooter, the son of two asylum seekers from Iran who came to Germany in the late 1990s, had been treated for psychological problems.

Police Chief Hubertus Andrae told reporters Saturday there were signs the gunman suffered from depression. There did not appear to be any link to the refugee issue plaguing Europe, he added.

The dead included three "youngsters," police said. Three people among the 27 injured in the attack remained in critical condition.

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The shooting began Friday evening outside a McDonald's restaurant in the northern section of the Bavarian capital and later erupted at the Olympia shopping mall.

Munich police investigator Robert Heimberger said the attacker apparently hacked a Facebook account and sent a message urging people to come to the mall for a free giveaway. Andrae said books about mass killings were found in the gunman's room, including one, by an American author, titled Why Kids Kill: Inside the Minds of School Shooters.

“Documents were found about mass shootings,” Andrae told reporters. “The perpetrator was obviously obsessed with the issue.”

The attacker's body was found less than a mile from the scene of the initial shooting. He used a Glock 9mm with a serial number that was illegally removed and carried a backpack with about 300 bullets inside.

The shooting induced panic among shoppers and prompted authorities to shut down streets, rail and metro traffic in the country's third-largest city. Residents were urged to stay indoors.

More than 2,300 security forces from across Germany and nearby Austria poured into the streets in an intense manhunt that included snipers perched in helicopters flying low over the city. Initial reports that up to three gunmen may have been involved in the attack turned out to be incorrect, police said.

A cellphone video posted online showed the person filming from a balcony engaging verbally with the suspect dressed in black standing on the rooftop of the mall parking structure, the Associated Press reported. The shooter at one point yells, “I’m German,” to which the filmer responds, “You are a jerk,” and demands to know what he is up to. The shooter yells at him to stop filming, and shortly after begins shooting. Andrae said police believe the video is genuine.

At an address on Dachauer Strasse searched by police early Saturday, a neighbor described the suspect as “very quiet.”

“He only ever said ‘Hi.' His whole body language was of somebody who was very shy,” said Stephan, a coffee shop owner who would give only his first name, according to the AP.

“He never came into the cafe,” he added. “He was just a neighbor and took out the trash but never talked.”

The attack was the third to target civilians in Europe in just over a week following a deadly assault in Nice that killed 84 people.

The rampage comes at an especially tense time for Germany. On Monday, an Afghan asylum seeker, also a teenager, went on a stabbing rampage with a knife and ax, injuring a group of Hong Kong tourists on a train near the Bavarian town of Wurzburg. It was the first attack to strike Europe's most powerful and wealthy country since German Chancellor Angela Merkel's decision to let in over a million asylum seekers from conflict zones such as Afghanistan and Syria last year.

Police said the Wurzburg attacker appears to have been inspired by the Islamic State, but they have not been able to establish any direct link to the extremist group.

As Munich struggled to return to normal Saturday, Mayor Dieter Reiter declared a day of mourning for the victims of “this terrible act.” German media reported Merkel cut short a vacation in the Alps to chair a national security meeting.

In the central part of the city, streets were quieter than usual and many smaller cafes and stores were closed. Some posted signs outside saying they decided to close out of respect for those killed and injured. The main train station was busy with tourists dragging suitcases across the main hall, but there was no extra police or security presence.

In the neighborhood where the attack took place, about four miles outside the center, police maintained a large presence, barring outsiders from getting close to the restaurant and shopping complex where the shots were fired. A few small makeshift memorials with flowers perched up against trees could be seen.

On the leafy, quiet streets behind the mall, groups of local residents stood around talking and consoling one another. "We're just in shock," said Jasmine Sendet, 23, a dental assistant who gathered on a street corner with four friends.

Sendet said she learned an old school friend of hers was one of the nine people gunned down Friday. She had not seen him in a while and was still processing his death.

"Every time there is violence now we are told it is probably because of the Islamic State. But they had nothing to do with this," she said. "We are very nervous."

Stanglin reported from McLean, Va.