(CNN) The teenager who shot dead nine people in Munich on Friday was a mentally troubled man who had extensively researched rampage killings and had no apparent links to ISIS, German police said.

Authorities said the 18-year-old lone attacker -- who died of a self-inflicted gunshot wound -- had no political motivations.

No references to religion were found in documents in his home in the southern German city.

But investigators searching his belongings found numerous documents on rampage killings, including a book entitled "Rampage in My Mind -- Why Students Kill," said Robert Heimberger, president of the Bavarian state criminal police office.

Neighbors ID gunman

Neighbors say it was Ali Sonboly's apartment that police searched.

Neighbors told CNN that the teen who lived in the apartment searched by police was Ali Sonboly. German police said the gunman's parents had been taken in for questioning.

Police have not named the attacker, but said he had dual German and Iranian nationality, and was born and raised in Munich.

It appeared that before the attack, the gunman had hacked a woman's Facebook account to post a fake offer of free food at the McDonald's branch where the attack began,German Interior Minister Thomas de Maiziere said.

Investigators were still working to confirm that he posted that to lure people to the scene.

significance in the timing of the attack, five years to the day since Police said there was also likely to besignificance in the timing of the attack, five years to the day since Anders Behring Breivik killed 77 people in Norway in 2011, many of them attendees at a youth camp.

Both attacks targeted young people, with most of the victims in Munich in their teens, Police Chief Hubertus Andrae said.

Attack targeted youth

Three of the victims were 14, two were 15, one was 17 and another 19, while a 20-year-old and a 45-year-old were also killed. Three were female.

The victims all were German nationals from the Munich area, officials said. Turkey's Foreign Ministry said three of the victims were also Turkish nationals.

Another of the victims was also a Greek citizen, Greece's Foreign Ministry said Saturday.

The attack left 27 people wounded, 10 of them with serious injuries, Andrae said.

Photos: Deadly shooting at Munich mall Police secure an underground transit station after a deadly shooting in Munich, Germany, on Friday, July 22. At least eight people were killed at a nearby shopping mall in what police officials said "looks like a terror attack." Police are still looking for the gunmen. Hide Caption 1 of 15 Photos: Deadly shooting at Munich mall Police officers escort people from the mall with their hands raised. Hide Caption 2 of 15 Photos: Deadly shooting at Munich mall Police tape blocks the entrance to Odeon Square. Hide Caption 3 of 15 Photos: Deadly shooting at Munich mall Police officers search a man outside the shopping mall where the shooting took place. Hide Caption 4 of 15 Photos: Deadly shooting at Munich mall Armed police officers arrive at the mall. Hide Caption 5 of 15 Photos: Deadly shooting at Munich mall The Olympia mall, located in a middle-class neighborhood in northern Munich, is the city's biggest shopping center. Hide Caption 6 of 15 Photos: Deadly shooting at Munich mall Police and firefighters are at the scene. Hide Caption 7 of 15 Photos: Deadly shooting at Munich mall A police helicopter flies over the mall. Hide Caption 8 of 15 Photos: Deadly shooting at Munich mall Police secure the entrance to a nearby transit station. Hide Caption 9 of 15 Photos: Deadly shooting at Munich mall Police officers respond to the shooting. Hide Caption 10 of 15 Photos: Deadly shooting at Munich mall Police secure the area of Karlsplatz. Hide Caption 11 of 15 Photos: Deadly shooting at Munich mall Streets were blocked by police near the mall. Hide Caption 12 of 15 Photos: Deadly shooting at Munich mall Police secure the area inside the mall. Hide Caption 13 of 15 Photos: Deadly shooting at Munich mall Police walk near the scene of the shooting. Hide Caption 14 of 15 Photos: Deadly shooting at Munich mall Many people started running when they heard the gunshots, said Lynn Stein, who works at the Jack Wolfskin store in the mall. Hide Caption 15 of 15

Gunman's fatal wounds self-inflicted

The gunman stormed the McDonald's outside the Olympia mall in Munich on Friday evening, before continuing in to the shopping center, bringing Germany's third-largest city to a standstill. Residents were warned to avoid public places and public transport was halted.

Authorities, initially fearing three gunmen were on the loose, mounted a massive operation involving 3,200 security personnel. Terrified shoppers sought safety in strangers' homes.

Police engaged in a shootout with the gunman, whose body was found near the scene of the attacks. An autopsy indicated he died of a self-inflicted gunshot wound, police said.

No suicide note had been found in the attacker's home, and his parents were too shocked to help police in their investigations, officials said.

The attacker used a 9 mm Glock 17 pistol that was likely obtained illegally. The serial number had been scratched off, and he had about 300 rounds of ammunition in his backpack, police said.

Attacker not known to authorities

De Maiziere said there had been no previous police or intelligence agency investigations into the attacker, the son of Shiite Muslims from Iran who came to Germany as asylum seekers in the 1990s.

"We know that in the apartment of the perpetrator, material was found which leads to him being interested in those who go on a rampage," he said. "We do not have any indications that would lead to international terrorism."

The attacker had received medical treatment for mental health issues, a police official said. In 2012, he had been the victim of "bodily injury" in an incident involving other young people.

Security jitters in Europe

The attack shook Europe after a spate of recent terror attacks on the continent, including the stabbing of passengers on a German train by a man who claimed to be inspired by ISIS, and the killing of 84 people in a deadly truck attack in Nice, France.

German Chancellor Angela Merkel addressed the ongoing public anxieties over the security climate as she expressed her condolences at a news conference in Berlin.

"We are mourning those who will never go back to their families," she said, before addressing the bereaved families of the victims of Munich's "night of horrors."

"We share your pain. We think of you. We suffer with you."

She expressed her gratitude for German security forces.

"We live together in a liberal society. This freedom is our greatest strength," she said.

'He's ... killing the children'

A witness who was in the McDonald's restaurant said her son was in the bathroom with the gunman.

"That's where he loaded his weapon," said Lauretta, who only wanted to be identified by her first name.

She said she saw many young casualties.

"I hear like an alarm and boom, boom, boom ... and he's still killing the children. The children were sitting to eat. They can't run."

Lauretta said she heard the gunman say, "Allahu Akbar," or "God is great" in Arabic.

"I know this because I'm Muslim. I hear this and I only cry," she said.

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'You will get it.'

Witness Huseyin Bayri said he was riding his bike outside the restaurant when he saw the attacker yelling.

"I heard a scream at first: 'You shitty ... foreigners. I am German. You will get it,'" Bayri said.

"And then the first shots were fired. And a boy of about 14 or 17 years of age ... collapsed, fell to the floor."

JUST WATCHED Teen kills 9 people in Munich shopping district rampage Replay More Videos ... MUST WATCH Teen kills 9 people in Munich shopping district rampage 01:24

Bayri jumped off his bike, crawled toward the wounded teenager and hid next to him. He tried to reassure him as he pressed on his gunshot wounds to stop the bleeding.

"The boy asked for my help. I tried to talk with him, asked him his name, his age, if he has a girlfriend," Bayri said. "I tried to make sure that he looked at me, that his eyes are open."

The teen pleaded with Bayri to call an ambulance, but died just before it got there.

From eatery to mall

After the shooting, the gunman moved across the street to the mall, which is near the site of the 1972 Summer Olympics where Israeli athletes were killed by Palestinian attackers.

Lynn Stein, who works in the mall, described a chaotic scene when gunfire erupted.

"People were very confused, and they were running and they were screaming," she said.

She saw someone lying on the floor of a store who appeared to be either dead or injured.

"There's a woman over them, crying," she said.

Verbal exchange

JUST IN: Twitter video shows people running from scene of shooting at German shopping center https://t.co/rI3HVFMiav pic.twitter.com/59Pf70D5cF — CNN (@CNN) July 22, 2016

Photos and video posted on social media showed a profanity-filled verbal exchange between a man on the top level of a parking garage and another one on a balcony.

The man who appeared to be a shooter said insulting things about Turks, did not espouse jihadist ideology and spoke with a German accent.

The conversation ended in gunfire.