Sonboly had an obsession with mass shootings and rampage killers ; he compiled a scrapbook of news clippings on mass shootings and owned several books on the matter . During his psychiatric treatment he repeatedly told fellow patients to refer to him as the ' Spree Killer ' . One incident that fascinated him was the Winnenden school shooting , and he visited Winnenden and took pictures there . Sonboly was also fascinated by the 2011 Norway attacks perpetrated by Norwegian terrorist Anders Behring Breivik , and Sonboly 's shooting was on its fifth anniversary
Winnenden school shooting
Winnenden school shooting
2016 Munich shooting