(CNN) -- A cold case in Alabama is heating up.
State law enforcement officials announced the indictment of a suspect Wednesday in a series of sex crimes committed against three young Alabama girls between 1999 and 2004.
Attorney General Luther Strange credited the state's unit that focuses on older, unsolved crimes for the arrest. "This case is an example of the excellent work performed on a regular basis by the Cold Case Unit," Strange said in statement.
A Calhoun County grand jury returned an indictment against former county resident Billy Wayne Cooper, 45, on May 6. Cooper is charged with a number of counts of rape, sodomy, and sexual abuse.
The victims were between 13 and 15 years old at the time of the crimes, which occurred in multiple locations, according to a press release from the attorney general's office.
"Since beginning its work, the Cold Case Unit has provided hope and delivered justice for many victims whose cases had long gone unsolved," Strange said.
The suspect is already serving time for convictions in other sexual attacks
Cooper is currently jailed at a detention facility in Fort Leavenworth, Kansas. He's serving a sentence for convictions in multiple sex crimes at U.S. Army posts in Washington state and Germany.
The Alabama charges carry a maximum penalty of life in prison.
Vivian Kuo contributed to this story