US President George Bush said tonight that mass shootings are a reminder that people must be willing to raise a red flag about others’ disturbing behaviour.

While the parents of the Virginia Tech gunman have kept silent and out of public view, his uncle met an official from a Korean-American association and said he "assumes" the parents are doing fine.

The gunman in the Virginia Tech massacre was a sullen loner known as “the question mark kid”, who alarmed professors and classmates with his twisted, violence-drenched creative writing.

Police hunting the Washington DC sniper are bringing in experts to hypnotise witnesses in the hope of jogging hidden memories.