A 16-year-old friend of Munich gunman, David Ali Sonboly, has been arrested in connection with the mass shooting that left nine people dead. The 18-year-old went on a rampage on Friday (22 July) at the Olympia shopping centre, based in the Moosach district of the Bavarian city, before turning his gun on himself.

Investigators have now arrested Sonboly's friend, under the suspicion that the Afghan teen may have known about the planned attack but failed to report it to authorities.

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The youth may also have played some part in sharing a Facebook post, in which people were lured to a McDonald's restaurant under the pretext of receiving free food.

Of the nine people dead, most were teenagers who were not personally know to Sonboly. Thirty-five people were also injured in the shooting spree. Three remain in a critical condition.

Police have been investigating claims that the killer lashed out in anger, seeking revenge for being bullied by his peers. Just weeks before the shooting, Sonboly had warned a 14-year-old girl living in his apartment block: "I will kill you all."

While police found no links with Islamist terror groups or any political motivation for the attack, it was revealed he was fixated with mass killings. It is thought he may have been inspired by Norwegian mass murderer, Anders Breivik, who killed 77 people in 2011, five years prior to the recent Munich shootings.

In 2015, Sonboly had travelled 250km (155.3 miles) to the site of the school shooting in Winnenden to take photographs of the murder scene. It emerged that he had been plotting the shooting for more than a year and purchased a handgun on the dark web which he used to carry out the atrocities.

Sonboly had a history of mental health problems and was a psychiatric inpatient in 2015, Sky News has also reported.

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