Police are investigating after the son of a senior US politician reportedly stabbed his father and then shot himself.

Three people were killed and 25 injured after a pile-up involving 95 vehicles on a foggy US highway.

The Virginia Tech gunman who shot dead a police officer then killed himself was a part-time college student.

A massive manhunt involving more than 100 police and helicopters with thermal imaging was under way today for a gunman who killed eight people in Virginia.