WASHINGTON (Reuters) - A 35-year-old former Blackwater security guard was found guilty of first-degree murder on Wednesday for shooting a civilian at a crowded traffic circle in the Iraqi capital Baghdad in 2007, an incident that drew worldwide condemnation.

Nicholas Slatten was convicted of killing Ahmed Haithem Ahmed Al Rubia’y, one of 14 civilians slain when Blackwater guards opened fire in Nisur Square on Sept. 16, 2007, the U.S. Attorney’s Office for the District of Columbia said in a statement.

Slatten is being held pending sentencing and faces a mandatory life prison term, the U.S. Attorney’s Office said.

His murder conviction came a year after a federal appeals court vacated his initial 2014 conviction, saying he should have been tried separately from three other Blackwater guards involved in the incident.

Prosecutors allege that Slatten, of Sparta, Tennessee, fired the first shots and intentionally set off a shooting rampage that killed or wounded 31 civilians, beginning with the death of the driver of a white Kia, Ahmed Haithem Ahmed Al Rubia’y, 19. The dead included 10 men, two women and two boys, ages 9 and 11.

The shooting stood out for its brutality even in a city in the grips of a bitter sectarian war, and sparked debate over the role of private security contractors such as Blackwater working for the U.S. government in war zones.

Slatten and his fellow guards were traveling in a heavily armed, four-truck Blackwater Worldwide convoy and had been trying to clear a path for U.S. diplomats after a nearby car bomb.

At Nisur Square, they opened fire on Iraqis, including women and children, with machine guns and grenade launchers.

The U.S. Justice Department has long pursued accountability for the Nisur Square shooting.

The Justice Department’s case against Slatten hinged on him having fired the first shots because of a general animosity toward Iraqis. But some evidence suggested an unnamed co-defendant might have fired the initial shots.

The appeals court also ordered the three other Blackwater guards to be resentenced, saying their 30-year terms were too long. That resentencing is pending, the U.S. Attorney’s Office said. Slatten had received life in prison in the initial conviction.

Blackwater, which was founded by former Navy SEAL Erik Prince, the brother of Education Secretary Betsy DeVos, was later sold and now operates as Virginia-based Academi.