Washington ? The Army is opening a criminal investigation into the friendly fire death of former NFL player Pat Tillman to probe whether negligent homicide charges should be brought against members of his Ranger unit who killed him in Afghanistan nearly two years ago, according to defense officials.

Pentagon officials notified Tillman’s family on Friday that a Defense Department Inspector General’s review of the case had determined there was enough evidence to warrant a fresh look, after initial investigations that were characterized by secrecy, mishandling of evidence and delays in reporting crucial facts about what had happened.

The Inspector General’s review was launched in August after bitter and public complaints by the Tillman family that the Pentagon had failed to hold anyone accountable for the April 22, 2004, shooting or to fully explain its circumstances. His mother, Mary Tillman, has expressed deep frustration about what she calls a succession of “lies” she has been told about her son’s death.

The Army originally reported that Tillman was killed in a firefight with enemy forces in the rugged mountains of Afghanistan near the Pakistani border, and officials heralded his heroism with a tale of how he was charging a hill against the enemy when he was shot.

Weeks later, after a nationally televised memorial service, the Army revealed that he had been gunned down by members of his own unit who rounded a corner in a Humvee and mistook him and a coalition Afghan fighter for the enemy.

Mary Tillman said Saturday that she thought evidence of a crime had existed all along, and that the family’s repeated calls for a criminal investigation were ignored until now.

“It is completely obvious that this should have been done from the very beginning,” she said. “The military has had every opportunity to do the right thing and they haven’t. They knew all along that something was seriously wrong and they just wanted to cover it up.”

Patrick Tillman Sr. expressed skepticism that the new investigation will yield additional answers.

“I think it’s another step,” he said. “But if you send investigators to reinvestigate an investigation that was falsified in the first place, what do you think you’re going to get?”

The loss of Tillman – a popular Arizona Cardinals football player before joining the military after the Sept. 11, 2001, terrorist attacks – rattled the Army in part because of the controversy over the nature of his death and the interactions with his family.

Another friendly fire incident just days after Tillman’s death, in Iraq, also included delays in notifying family members and confusion about what happened. Army officials have been working to improve the information flow to families of soldiers who die in Iraq and Afghanistan.

Col. Joseph Curtin, an Army spokesman at the Pentagon, said the Army would open an investigation to examine whether soldiers violated military law when they failed to identify their targets before opening fire on Tillman’s position.

Although there have been several military investigations into the Tillman shooting, this will be the first criminal investigation. A defense official said that it likely would focus on the potential charge of negligent homicide, which means investigators will try to determine if soldiers fired recklessly without intending to kill their fellow soldier.

“We want to do the right thing for the family,” Curtin said. “We owe it to the family. We owe them the truth.”