The commander of a US army base where a soldier shot three colleagues says an "escalating argument" was the most likely cause of the attack.

Special Operations Marine MacPherson (Val Kilmer) is badly wounded during a tour of duty in Iraq and returns home, where he descends into a morass of despair and self-loathing.

US President George Bush today signed a bill authorising 700 miles of new fencing along the US-Mexico border, hoping to give Republican candidates a pre-election platform for asserting they are tough on illegal immigration.

A Republican Congressman wants to build a fence along the entire 2,000-mile US-Mexico border, a plan that could cost billions of dollars and one that critics say would do little to stop illegal immigration.