The official version of last week's Fort Hood massacre may have to be revised after it emerged that the shots which brought down the alleged gunman were probably fired not by a petite policewoman but by her male partner.

Sergeant Kimberly Munley was hailed a heroine around the world after officials credited her with bringing down Major Nidal Hasan after he opened fire in a processing centre at the sprawling military base on Texas.

But a witness to the shootings, in which 13 people were killed, has told The New York Times that Sergeant Munley was herself shot almost as soon as she arrived at the scene.

The witness, who asked not to be identified, said that Major Hasan then turned his back on the policewoman and started to reload his semi-automatic FN rampage pistol.

"It was at that moment that Senior Sgt Mark Todd, a veteran police officer, rounded another corner of the building, found Major Hasan fumbling with his weapon and shot him," the newspaper reported today.

At a press conference at Fort Hood yesterday, a military spokesman, Lieutenant-Colonel John Rossi - who last week paid tribute to Sergeant Munley's professionalism - refused to address the issue of which officer filed the crucial shots.

“These questions are specific to the investigation and I am not going to address that,” Colonel Rossi told reporters. The Pentagon said the answer would depended on the results of ballistics tests.

Both Sergeant Munley and Sergeant Todd appeared on NBC's Today programme this morning where they were questioned closely about the sequence of events - but neither could confirm exactly what happened.

Sergeant Munley insisted that she had fired at the gunman, but could not say whether she had hit him. Sergeant Todd described firing the shots which brought down Major Hasan - the first he had ever fired at a live target in a 25-year career - but could not say whether the gunman had already been hit.

Despite the disparity, there appeared to be no tension between the two partners as to who should be given the credit for stopping the shooting spree: they were happy to share the praise.

In its story, The New York Times compared the official version of events with that of Private Jessica Lynch, who was captured during the invasion of Iraq in March 2003. Pentagon press releases spoke of how she had fought back against her capture; in fact she had been knocked unconscious when her vehicle crashed in an ambush.

In an interview with the newspaper, Sergeant Todd’s wife, Lisa, said that he had asked the army to protect his identity in the immediate aftermath of last week's shootings. Her husband did not consider himself to be the real hero of the day, she said. “They were in this together,” she said.

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