Military Officials conceded at the weekend that a former American football star, who left his multimillion-dollar career to join the armed forces after the 11 September attacks and was killed in action in Afghanistan last month, was probably a victim of "friendly fire".

Military Officials conceded at the weekend that a former American football star, who left his multimillion-dollar career to join the armed forces after the 11 September attacks and was killed in action in Afghanistan last month, was probably a victim of "friendly fire".

The death of Corporal Patrick Tillman on 22 April shocked the US and was a reminder to many Americans of the continuing perils for soldiers in Afghanistan as well as Iraq. At the time, the US Army said he had been shot by enemy fire while on patrol south-west of Khost, near the Pakistan border.

Giving few details, the Army offered the revised version of his fate after reports that he may have been killed by "friendly fire" surfaced in newspapers in Arizona on Saturday. Before signing up, Cpl Tillman played for the Arizona Cardinals with a contract worth $3.6m (£2m) a year. He served in Iraq last year and was sent to Afghanistan on a second tour of duty.

"While there was no one specific finding of fault, the investigation results indicate that Cpl Tillman probably died as a result of friendly fire while his unit was engaged in combat with enemy forces," Lieutenant-General Philip R Kensinger told reporters at the Army Special Operations Command at Fort Bragg.

Cpl Tillman's status as a national hero will be hardly dented by the new details of his fate. It is an embarrassment for the US military, however, which had earlier given a fairly detailed account of the events leading up to his death. In that version, Cpl Tillman was said to have died after the second unit in a two-unit convoy came under attack and he turned back with his men to help his comrades.

"Through the firing, Tillman's voice was heard issuing fire commands to take the fight to the enemy on the dominating high ground," read an army citation when the soldier was awarded the Purple Heart and Silver Star posthumously for valour. "Only after his team engaged the well-armed enemy did it appear their fires diminished."

It now appears that an Afghan soldier who was alongside Cpl Tillman as they returned to the first unit was mistaken as an enemy combatant by one of the US soldiers and fired upon. Other US soldiers began shooting in the same direction, at which point Cpl Tillman was fatally wounded. It seems, moreover, that there were no enemy soldiers in the vicinity at the time.

At a memorial service for Cpl Tillman held earlier this month, tributes were led by Senator John McCain, who was held as a prisoner-of-war in Vietnam. "While many of us will be blessed to live a longer life, few of us will ever live a better one," the senator said.

Among those who were insisting that the heroism of Cpl Tillman remained untarnished were officers at Fort Bragg, where his unit was based. "A lot of us sacrifice something, but no one sacrificed as much as he did to join," Sergeant Matt Harbursky said. "And it doesn't really matter how he was killed; it's sad."