(CNN) -- Jury selection begins Tuesday in the retrial of two U.S. security contractors accused of killing two Afghanistan civilians.

In September, a federal judge declared a mistrial in the case against Christopher Drotleff and Justin Cannon after the jury in the case said they were unable to reach a unanimous verdict.

Drotleff and Cannon worked as security contractors for a subsidiary of Xe, the military contracting firm formerly known as Blackwater Worldwide.

Each were charged with two counts of second-degree murder and one count of attempted murder in connection with a May 2009 shooting in Kabul, Afghanistan.

The 12-count, 19-page indictment returned by a federal grand jury in U.S. District Court for the Eastern District of Virginia also included weapons charges against the two men.

Both Drotleff and Cannon were in Afghanistan working for the security company Paravant -- a subsidiary of Xe -- to help the U.S. Army train Afghan troops.

Drotleff, Cannon and two other contractors, Steven McClain and Armando Hamid, were driving their interpreters on a busy Kabul street called Jalalabad Road on May 5, 2009, when they said a car slammed into one of their two cars.

The men said they got out to help their colleagues, and the vehicle that had struck the car did a U-turn and headed back at them.

The contractors said they fired at the oncoming vehicle in self-defense.

The incident spotlights the issue of the role and conduct of U.S. security contractors in Afghanistan.

A similar issue arose in Iraq after a September 2007 confrontation involving then-Blackwater contractors that left 17 Iraqi civilians dead.

Blackwater lost its contract there after Iraq's government refused to renew its operating license. The company then changed its name to Xe.