MONTPELIER, Vt. — Canadian Pte. Robert Costall and an American soldier were shot from behind by bursts from a machine-gun fired from a compound manned by U.S. special forces last year in Afghanistan during an insurgent attack, a U.S. army report says.

One account in the report says the gunner shot at two friendly positions in quick succession during the fierce battle early on March 29, 2006.

The friendly fire killed the two soldiers and wounded a number of others at Forward Operating Base Robinson in Afghanistan's Helmand province.

The army report was released to The Associated Press on Monday. It contains a collection of witness statements assembled by American investigators.

Costall, a 22-year-old machine-gunner, was born in Thunder Bay, Ont., and grew up in Gibson, B.C. The possibility of him being killed by friendly fire was raised earlier by his wounded comrades.

The U.S. army report presents witness statements that support those reports.

It says Sgt. John Thomas Stone of the Vermont National Guard was shot once in the back and once in the head by machine-gun rounds while crouching behind a wall atop a building where he and other allied troops were repelling a major night-time attack.

The friendly fire from behind also killed Costall and wounded others defending the base, according to the report.

Earlier Canadian reports said Costall was also felled by two bullets.

His platoon, of 1st Battalion Princess Patricia's Canadian Light Infantry, was rushed in as reinforcement to the outpost that had come under a series of attacks by insurgents.

A first sergeant referred to as Witness 1 in the report says: "When the majority of the firefight took place (at) approximately 02:15, the (Special Forces) security element in the northeast corner began shooting out toward the perimeter, I immediately realized the S.F. was shooting at the Canadian position.''

Witness 1 said he whistled to signal the Special Forces soldiers to stop firing.

"The S.F. Security then turned his weapon 100 to 140 degrees from its original position and began firing in the direction of the American ETT compound,'' the witness said -- referring to the location where Stone, an embedded tactical trainer, was hit.

Investigators found a string of bullet holes from the gunner's location to the wall that Stone and others were using as cover from enemy fire from outside the base.

The report includes statements from some Special Forces soldiers at the battle, but, not apparently from the soldier believed to have fired the M240 machine-gun that killed Stone and Costall.

The report does not indicate whether anyone was disciplined.

It did not have any statements from the Canadian soldiers present.

A separate investigation into the incident was ordered by the Canadian Forces National Investigative Service.

A spokesman for the U.S. Special Operations Command at Fort Bragg, N.C., said he was unaware of the report and could not immediately answer questions about it.

The report detailed how Americans and Afghan soldiers at Forward Operating Base Robinson were expecting to be attacked that night in retaliation for a coalition attack on enemy forces in the area.

A group of about 30 Canadian soldiers was brought in that day as reinforcement. The Canadians were positioned behind a berm at the northeast corner of the compound.

Stone was sleeping when the attack began with mortar rounds just before 2 a.m.

Small-arms fire followed. Stone went to the roof of the building where he was staying when the fighting started.

An Army captain was wounded on the roof not far from Stone. Soldiers tending to the captain found Stone slumped against the wall, apparently killed instantly by the bullets that hit him.

Another witness said Stone's body armour was found underneath his bed.

Stone's comrades were immediately aware that the shots that hit him and wounded the others came from behind them.

The U.S. Central Command in Florida released the report in response to a Freedom of Information Act request by the AP.

Other than Stone and Costall, all names were blacked out in the report.

The report also excluded, on grounds of national security, information collected by an unmanned Predator aircraft and certain log entries by the duty officer.

After his death, Stone, 52, was promoted to master sergeant. He was on his third tour in Afghanistan when he was killed.

Several days after Stone's death the National Guard announced that an investigation had begun to determine if he was killed by friendly fire. The report was not completed until April of this year and Stone's family was briefed in early May.

"The preponderance of evidence in the report indicates that Master Sergeant Stone was the victim of friendly fire,'' said Guard spokesman Capt. Keith Davio.

"We have met with members of his family and have done everything we possibly could to answer their questions. We hope this provided some measure of closure for them and we ask that their privacy be respected.''