A federal grand jury has added an additional indictment to a former Blackwater employee involved in the murders of two Afghan civilians in May of 2009, according to The Virginian-Pilot.

Two Blackwater guards have been charged with second-degree murder for the fatal shootings.

The Virginian-Pilot reports,

[Christopher] Drotleff, of Virginia Beach, and [Justin] Cannon, of Corpus Christi, Texas, were working for a subsidiary of Blackwater, also known as Xe, to train the Afghan police force in Kabul. The indictment alleges they were drinking that day when they became involved in a traffic accident and began firing their weapons at another car.

Drotleff and Cannon say they fired in self-defense, in fear for their lives, at a car that was speeding toward them. The government counters that the victims were all shot from behind.

The new indictment replaces a firearm charge against Cannon with use of a machine gun during the killings. The new charge carries a mandatory minimum sentence of 30 years in prison on conviction.

The two former Blackwater security workers were also charged with aiding and abetting each other in the murders of Rahib Mirza Mohammad and Romal Mohammad Naiem. A third civilian, Fareed Haji Ahamd, was wounded in the shooting.

Drotleff and Cannon will appear before the grand jury for trial on September 14.

A similar incident occurred in 2007, when five Blackwater security workers shot and killed Iraqi civilians in Baghdad.

The five guards, who had been part of a convoy of armored vehicles, had been charged with killing 14 unarmed Iraqi civilians and wounding 18 others during an unprovoked attack at a busy Baghdad traffic circle using gunfire and grenades.

The men had faced firearms charges, and up to 10 years in jail on each of 14 manslaughter counts, but a judge dismissed the case.

In 2009 Blackwater Worldwide officially changed its name to Xe, in the midst of widespread negative publicity.