THE investigation of a shooting spree that left nine people and the gunman dead on a Minnesota Indian reservation took a new turn when a source familiar with the probe said the tribal chairman's teenage son was arrested.

A teenager has been arrested in connection with last week’s shootings on a Minnesota Indian reservation, according to a police source.

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.