The Munich shooting had killed nine people and injured 16 others.
Germany is reeling after a teenager went on a shooting spree at a Munich shopping mall, killing nine people and wounding 16 others before turning the gun on himself.
The gunman, a German-Iranian named David Ali Sonboly, suffered depression and was obsessed with shooting sprees like the 2011 massacre by Norwegian rightwing fanatic Anders Behring Breivik.
Officials stressed that Sonboly, 18, had no links with the ISIS jihadist group.
A picture is emerging of a lonely young man with a history of mental illness. The interior minister said Sonboly had probably been bullied.
Born in Munich to Iranian parents, neighbours described him as quiet and polite, while a police source told DPA news agency he was a fan of violent video games.
Investigations of his home and police files point to "a classic act by a deranged person," said Munich police chief Hubertus Andrae.
"There is absolutely no link to the Islamic State," he said, adding that the suspect had been obsessed with books and articles about mass killings "linked to maniacs".
The city's chief prosecutor also said the suspect had suffered "some form of depression", but voiced caution over reports he may have undergone psychiatric treatment.