Washington, April 14 (RHC)-- A court in the United States has sentenced 4 former guards with private security firm Blackwater to lengthy prison terms over their roles in the 2007 killing of 17 unarmed Iraqi civilians.

One of the four, Nicholas A. Slatten, who fired the first shots, was sentenced to life in prison while the others -- Dustin L. Heard, Evan S. Liberty, and Paul A. Slough -- got 30-year jail terms at the Monday court session in Washington.

Last October, they were convicted of a series of charges ranging from first degree murder to voluntary manslaughter during the fatal incident, which took place while they were escorting a diplomatic convoy in Nisour Square of the Iraqi capital Baghdad.

In September 2007, the Blackwater guards used sniper rifles, machine guns, and grenade launchers on unarmed Iraqis in the bustling square, killing 17, including children.