The U.S. military in Afghanistan says that Sunday's downing of a civilian helicopter was the work of a single gunman.
Lieutenant Colonel Matt Beevers, a spokesman for U.S. forces in Afghanistan, says evidence indicates the shooting down of the helicopter was done by an individual rather than an insurgent force.
He added that further details would be released once the investigation concludes.
"I think it is important to say that this was a lone assailant attacking the very folks that are here doing great work for the people of Afghanistan," he said.
The helicopter had been part of a postwar reconstruction project in the country's southern Kandahar province.
Colonel Beevers praised the work of Afghan authorities in investigating the attack, saying it showed a significant ability to maintain order in the war-ravaged nation.
"I think this really demonstrates the ability of the Afghan security forces in that area to move quickly, to seal off the area, to conduct an investigation, make arrests," said the American officer.
Remnants of Afghanistan's former hard-line Taleban regime had initially claimed responsibility for the incident, which claimed the life of the Australian pilot and injured two passengers.
The Taleban have been leading an armed insurgency against the Afghan transitional government, although their attacks on Afghan and U.S. targets have dropped in size and frequency over recent months.
Afghan President Hamid Karzai said in an interview published in the Pakistan News that his administration hopes to reintegrate Taleban members back into society.
He added these efforts would not extend to those few who had committed crimes against the nation, but did not specify exact criteria for pardoning former Taleban.