SYDNEY (AP) — Australia's army failed to provide adequate security for three Australian soldiers killed in Afghanistan last year by an Afghan army colleague, the nation's defense department concluded in a report released Wednesday.

On Aug. 29, 2012, a group of Australian soldiers were playing cards in an administration area of a base in Uruzgan province when a man in an Afghan army uniform opened fire with an automatic weapon, killing three and wounding two. The Afghan soldier accused of the shooting, Sgt. Hekmatullah, fled and has not yet been caught.

The defense department's inquiry found that in the lead-up to the attack, the level of security was too weak given the Afghan army's open access to the administration area and the Australian soldiers' relaxed disposition; many were not wearing body armor.

"The inquiry officer found the decisions and actions in establishing and maintaining the force protection arrangements were at the minimum level of authorized protection to provide security for the soldiers," Air Marshal Mark Binskin, vice chief of the Australian Defense Force, told reporters in Canberra. "However, they did not adequately address the specific situation at the patrol base that potentially placed personnel at significant risk to the threat of fire."

Three Australian soldiers are expected to be disciplined over the security gaps, Binskin said, declining to specify how severe the punishment would be.

Whether the security shortfall directly led to the attack is unknown, the report said, and Binskin said there's no guarantee better protection would have saved lives.

"No matter how much you put in place you can never, 100 percent stop someone trying to commit a crime like this," he said. "You can mitigate the risk as best you can, but I don't believe you could ever stop someone who is intent on doing this."

The inquiry found that there had been no intelligence prior to the shooting to suggest an imminent threat, and the atmosphere between the Afghan and Australian soldiers at the base had been good.

Still, Australian officials knew there had been a spike in so-called insider attacks, in which Afghan security forces or insurgents posing as soldiers or police fire on their coalition allies. In 2012, 62 personnel were killed in such attacks, versus 35 a year earlier, according to NATO.

Binskin said the shooter's motivations are still unclear.

Australia has 1,550 troops in Afghanistan and makes the largest military contribution of any country outside NATO.