University authorities at the centre of America's worst campus massacre are facing criticism over their handling of the shooting. Questions remain over how a gunman apparently evaded detection after killing two people at a residence hall and then went on to kill 30 others two hours later in another part of the sprawling Virginia Tech campus. Many students expressed anger that they were not warned of any danger until more than two hours after the first attack, and then only in an e-mail from the university. The lone gunman, confirmed as a student of Asian origin, killed himself in a classroom before law enforcement officers reached him.