According to police, the gunman was fascinated by school shootings, but his motive remains a mystery.
After killing 10 people at the BORG Dreierschützengasse high school in Graz, the perpetrator killed himself. He left the school three years earlier.
The incident in Austria's second-largest city was the deadliest mass shooting in the country's recent history.
Although his motive for the attack remains unclear, investigators can “say with certainty that, over the years, he developed a passion for school shootings,” said Michael Lohnegger, the head of Styria province’s criminal police office.
“He glorified not just the acts in general, but also the perpetrators who carried out these acts."
The gunman had planned the attack meticulously, according to investigators, but they did not know why he chose the date he did for the massacre or why he stopped shooting when he did - the gunman still had many additional bullets.
The shooter had no prior criminal record. During a search of his house, police found plans for an explosive attack as well as a non-functioning pipe bomb.
Officers also discovered a digital and handwritten suicide note addressed to his parents, although the Director of Public Security Franz Ruf said that it offered no motive.
Nine of the 11 people wounded in last week’s attack remain in hospital, Lohnegger said on Tuesday, adding that they were not in critical condition.
The shooter used two firearms he legally owned to carry out the attack. On Monday, Chancellor Christian Stocker vowed to tighten Austria’s gun laws.
In the wake of the attack, the mayor of Graz, Elke Kahr, called for a complete ban on private weapons. Gun licenses are "issued too quickly," she said last week.
