IN HER FIRST TELEVISION INTERVIEW, MARY TILLMAN SAYS THE GOVERNMENT STILL HASN'T TOLD THE WHOLE TRUTH ABOUT HER SON PAT'S DEATH IN AFGHANISTAN -- "60 MINUTES"

Seven military investigations and two Congressional hearings can't convince Mary Tillman that the government is telling all it knows about the death of her son, a corporal in the U.S. Army Rangers. In her first television interview, Tillman talks to Katie Couric about her son, Pat Tillman, a former NFL star, and her frustration over the way the government handled information about his death by friendly fire. The interview will be broadcast on 60 MINUTES Sunday, May, 4 (7:00-8:00 PM, ET/PT) on the CBS Television Network.

"Well, it's hard to take when we heard it was a friendly fire.... I...didn't go into immediate...'Oh, these awful men, they need to be punished,'" says Tillman. "I felt terrible for these young men...and I still do -- to a degree. But I don't think it was the horrible accident that they like to play this out. I think there was huge negligence involved here," she tells Couric. Click here to watch an excerpt.

Four years ago in a canyon in Afghanistan, Cpl. Tillman, who gave up his professional football career to fight the war on terror, was killed. The initial word from the Army was that he died in an ambush trying to protect his men. It then came out weeks later that his own men had shot him. Mary Tillman has been on a crusade for the truth ever since, accusing the government of using the initial story as a publicity stunt and covering up the friendly fire incident.

She points to inconsistencies, including that his uniform was burned after his death, which is against regulations, and that the coroner refused to sign the autopsy for months because his analysis of Tillman's gunshot wounds was not consistent with the Army's original story.

The government doesn't blame her for thinking the worst and has apologized to her. Says Pete Geren, the secretary of the Army who ordered the latest Army investigation. "We made mistake after mistake. We failed in our duty to her. But, we've had seven investigations...a congressional investigation and they have all concluded that there was no deceit -- no intentional deceit -- no cover-up," he tells Couric.

Six officers and seven Rangers were disciplined for mistakes they made during the ambush and in the investigations afterward. Tillman is convinced there's more to the story. "It's just not the truth...and you want people to take responsibility for what they did," she says.

Tillman believes anything less than the truth dishonors her son and she will continue to pursue the matter. "I think that is what is sad about what has happened....Pat was a pretty honest guy. He wanted people to tell the truth, he tried to tell the truth. And he would want us to do this," she tells Couric.