The teenage gunman who shot and killed nine people and wounded 27 others on 22 July, reportedly used Facebook to lure in victims to a McDonald's outlet at a mall in Munich, the police said.

The teen shooter had apparently set up a fake Facebook account, posing as a teenage girl with the name "Selina Akim" and posted messages inviting people to the McDonald's outlet in a shopping mall.

It is unsure how many people, if any, fell for the ploy. An acquaintance of the shooter, Lukas Dore, had also cautioned people about the account being fake, warning Facebook users to steer clear of the promises made, the Telegraph reported.

"This here is a fake account of one Ali Sonboly. Don't get your hopes up," he wrote, adding: "The boy is psychologically disturbed and only wants attention."

The shooter, David Ali Sonboly, aged 18, reportedly launched a shooting rampage as revenge for having been bullied. Bavarian authorities said that Sonboly had a history of psychological issues and had spent two months at a clinic to receive psychiatric treatment.

The message read: "Come today at four o'clock to McDonald's at OEZ [shopping centre]. I am giving away anything you want as long as it's not too expensive."

Most of the victims were teenagers, with the oldest being a 45-year-old mother of two. It is believed that Sonboly specifically targeted youngsters belonging to "Turkish and Arab" origins, after having claimed to have been bullied by his peers in those groups when in school.

Sonboly allegedly illegally bought the murder weapon – a Glock pistol – from a dark net website. A 16-year-old friend of Sonboly has been picked by the Bavarian police in connection with the shooting. He is suspected to have played a part in sharing the Facebook messages posted by Sonboly that were aimed at luring victims.

Authorities said Sonboly appeared to be acting alone and have not yet found any connections to Islamic State (Isis) or any other extremist group. It has also become apparent that Sonboly had previously researched mass shootings. "There was material found in the apartment of the suspect that showed a particular interest in shooting sprees," said Interior Minister Thomas de Maiziere, the Mashable reported.

After the shooting, German chancellor Angela Merkel said: "Such an evening and such a night is difficult to bear. And it's even more difficult to bear because we have had so much terrible news in so few days."

Munich shooter used Facebook to lure victims into McDonald's outlet in mall
Candles and flowers laid in front of the Olympia shopping mall where a shooting rampage claimed 9 lives, in MunichReuters