Investigators have raided the house of the 21-year-old shooter who opened fire at his former school and have found a farewell letter and a makeshift bomb in the Austrian city of Graz. The incident left 10 people dead, and the perpetrator took his own life in the school toilet. The motive behind such an act remains quite nebulous, as Austrians mourned the victims with a minute of silence planned on Wednesday morning, as reported by AP. The shooter was a former student at the BORG Dreierschützengasse high school in Austria’s second-biggest city of Graz. Officials have acknowledged that the letter was found on Tuesday night, but the content of the letter did not allow them to draw definite conclusions. Austria’s public security director at the interior ministry, Franz Ruf, told ORF public television that a letter was found in both digital and analog forms where he bid farewell to his parents, but “no motive can be inferred from the farewell letter, and that is a matter for further investigations.”When asked whether the attacker chose the victims at random or targeted them specifically, Ruf said the matter is still being investigated, and they did not want to speculate.State broadcaster ORF, quoting local media, reported that the victims included both teachers and students. Multiple shots were fired, and the assailant had two weapons with him, a handgun and a shotgun, which apparently he owned legally. This appears to be the deadliest attack since World War II, with 11 people killed and over a dozen others injured.