According tto what I read, Rudakubana was not driven by an alleagance to any specific terrorist cause or organisation, but had an obsession with extreme violence and wanted to commit it. He accessed terrorist sites from a range of organisation because of the information they had on how to commit violent acts, and it was his obsession with violence that led to the referral to prevent, not any terrorist link. This act was not a terririst act.
However whether his act was driven by a terorrist alleagance or not, it beggars belief that someone with his clear obsession with violence, his violent behaviour which was known to schools and the police was allowed to go on for so long. I understand he has been diagnosed as autistic, and up thread there was a mention of schizoprenia, he should have been sectioned.
When we hear of autistic people whose only violence is directed against themselves being kept in hospital, often in solitary confinement for years. I cannot understand why this young man had never been sectioned and locked up.