Authorities were today trying to determine what caused a teenager to gun down his grandfather, put on the man’s police-issue belt and bullet-proof vest, and drive his marked squad car to a high school, where he began shooting his classmates at will.

THE suspect in the worst US school massacre since Columbine smiled and waved as he gunned down five students, a teacher and a guard, asking one of his victims whether he believed in God, witnesses said.

A neo-Nazi teenager who called himself the Angel of Death killed his grandfather and then stole his weapons and police car before embarking on a bloody shooting spree at a United States school, it emerged tonight.

A neo-Nazi teenager who called himself the Angel of Death went on a shooting rampage on a remote US Indian reservation yesterday, killing his grandparents and then seven people at his school, grinning and waving as he fired.