"Who does this?" the former Arizona Cardinals player wrote in a journal entry dated July 28, 2002, that is quoted in John Krakauer's book "Where Men Win Glory: The Odyssey of Pat Tillman," which hits book stores Tuesday. "Who takes a perfectly perfect life and ruins it? A perfectly happy wife and marriage and jeopardizes it? Ahhh! If I do not strangle someone while I'm here, I was touched by an angel."
A few months earlier, Tillman had written to his family that his life "at this point is relatively easy" and that he could "create a very comfortable lifestyle" playing football for several years.
"For more reasons that I care to list, my job is remarkable. However, it is not enough," he wrote.
Krakauer, who never met Tillman, told ABC News in a recent interview reported Friday, it was when he started researching his book that he realized Tillman's "depth and his complexity."
"He was much more than a football player or a patriot or any of that. He was all those things. But he was a remarkable human being," Kraukauer said.
Tillman was playing for the Cardinals when he decided to enlist at age 25 after the Sept. 11, 2001, terrorist attacks on the United States. He died April 22, 2004, while serving in Afghanistan as a corporal in the U.S. Army Rangers.