Ballard's mother, Karen Meredith, of Mountain View, Calif., has become a public critic of the war. Last month she was in Crawford, Texas, at a memorial erected by Veterans for Peace as part of the protest that began Aug. 6 outside President Bush's ranch by grieving mother and peace activist Cindy Sheehan.
Efforts to contact Karen Meredith on Saturday were not immediately successful.
Army officials said the failure to notify the family of the true cause of Ballard's death was an oversight. The military sometimes incorrectly categorizes the cause of war deaths. What is so unusual about the Ballard case is that the error was recognized early but not reported to the family for more than a year.
On Memorial Day in 2004, the day after Kenneth Ballard died, the Army informed his family that he had been killed by enemy fire while on a combat mission in the south-central Iraqi city of Najaf. In a casualty announcement from June 1, the Pentagon said Ballard died "during a firefight with insurgents." The military did not elaborate.
The Army disclosed on Saturday that Ballard, 26, actually died of wounds from the accidental discharge of a M240 machine gun on his tank after his platoon had returned from battling insurgents in Najaf.
He was buried at Arlington National Cemetery last Oct. 22.
An Army spokesman, Col. Joseph Curtin, said in an interview that separate investigations by the local commander and by the Army's Criminal Investigation Division concluded days after Ballard's death that it was an accident.
The tank accidentally backed into a tree and a branch hit the mounted, unmanned machine gun, causing it to fire, Curtin said. Ballard was struck at close range and died of his wounds, he added.
For reasons that are not clear, the Army did not correct the public record and inform the family until Friday.
Curtin said the matter was a regrettable mistake and that the Army's top civilian official, Francis Harvey, has ordered a review of procedures in reporting accidental deaths. He said a personal letter of explanation from Harvey was hand-delivered to the family on Friday.
"Furthermore, the Army regrets that the initial casualty report from the field was in error as well as the time that it has taken to correct the report and to inform his family," Curtin said in a prepared statement issued Friday night.
Ballard was a platoon leader in 2nd Battalion, 37th Armor Regiment, 1st Armored Division. During the Najaf fighting he was attached to a unit of the 2nd Armored Cavalry Regiment.
On May 22, approaching the one-year anniversary of her son's death, Meredith wrote in a Web posting, "One year ago you were killed by a snipers bullet. They said you were killed instantly. There is not a minute that goes by that I do not remember answering the phone and hearing I regret to inform you."
The 1st Armored Division, which also investigated the death, said in a written statement from its post in Wiesbaden, Germany, on Friday night that investigations had "revealed additional information of the cause" of Ballard's death. It did not mention that the investigations were conducted more than a year ago.
"These new findings in no way diminish Lt. Ballard's heroism, leadership or sacrifice to the nation and the people of Iraq," Maj. Gen. Doug Robinson, the 1st Armored Division commander, was quoted as saying. "We honor his service and offer our condolences to his family. He is an example of honor and heroism for all soldiers to emulate."