Walker, 28, was found Friday after hanging himself in his prison cell at the U.S. Disciplinary Barracks on Fort Leavenworth. He was taken to a hospital in Kansas City, Mo. where he died Sunday night.
Walker was an instructor in basic training at Joint Base San Antonio-Lackland where he had illicit relationships with as many as 10 women in training. Witnesses testified the former staff sergeant was "sadistic and manipulative" and used his authority to obtain sexual favors from recruits.
The Air Education and Training Command was notified of his death Tuesday.
"We are aware of Airman Basic Walker's passing and our thoughts are with the Walker family during this difficult time," Col. Sean McKenna told the San Antonio Express-News.
He was found guilty of seven charges and 28 specifications of misconduct, including rape, and was sentenced to 20 years in prison.
His case and the surrounding investigation exposed the widespread problem of rape culture and broken leadership in the U.S. military.