WASHINGTON 

A federal judge Wednesday sentenced a former Blackwater security guard to life in prison for his role in killing unarmed civilians in Iraq more than a decade ago. 

Nicholas Slatten, 35, was given a life sentence by U.S. District Judge Royce Lamberth without the possibility of parole after being found guilty of first-degree murder by a jury in December.

Three other ex-Blackwater security guards were found guilty of voluntary manslaughter and attempted manslaughter.

In 2007, Slatten and other Blackwater guards opened fire at a traffic circle in Baghdad, killing 14 civilians, including 10 men, two women and two young boys. The shooting left 17 others injured.

According to prosecutors, Slatten was the first to open fire, killing Ahmed Haithem Ahmed Al Rubia'y, who had been driving his mother to an appointment.

Slatten previously received a life sentence in 2014, but a federal appeals court ordered a mistrial.