What are the theories on the motive for the Örebro shooting?

Swedish police investigating the Örebro campus shooting are still hunting for clues that could explain why 35-year-old gunman Rickard Andersson carried out his deadly rampage.

What are the theories on the motive for the Örebro shooting?
Swedish police investigating the Örebro campus shooting are still hunting for clues that could explain why 35-year-old gunman Rickard Andersson carried out his deadly rampage.