Police in the US are hunting a second suspect following a shooting spree in Arizona that left six people dead.
Thirteen people were injured including Congresswoman Gabrielle Giffords who was shot in the head as she met with constituents in Tucson. The 40-year-old Democratic lawmaker was in critical condition and doctors were cautiously optimistic she would survive.
The 22-year-old suspect was apprehended at the scene but detectives believe he was possibly assisted by another person.
Pima County Sheriff Clarence Dupnik said the suspect "has kind of a troubled past and we're not convinced that he acted alone." He said he believed Giffords was the intended target of the shooting.
Dupnik said the suspect had made threats to kill in the past but not against Giffords. "All I can tell you is that this person may have a mental issue," he added, describing him as unstable.
A nine-year-old girl and a federal judge were reportedly among the fatalities following the attack which took place outside a busy supermarket on Saturday afternoon.
The shooting shocked Washington, where Congress postponed a key vote on healthcare reform scheduled for later this week. It was not known if the shooting was connected to any political stance.