Congresswoman Gabrielle Giffords remained heavily sedated and in a critical condition today as investigators sought to understand what motivated a gunman to carry out the assassination attempt in a rampage that left six people dead.

An assassination attempt has left a Democratic congresswoman in a critical condition, killed Arizona’s chief federal judge and five other people and forced Americans to question the toxic legacy of their divisive politics.

A US congresswoman was fighting for her life today after being shot in the head outside an Arizona supermarket as she met constituents.